This information will assist you in tracking down emission or driveability problems since the displays can be viewed while the vehicle is being driven. Refer to the Powertrain On Board Diagnostic (OBD) System Check for additional information.

Engine Data 1

Engine Speed - Range 0-16384 RPM: The VCM computes the Engine Speed from the fuel control reference input. The speed should remain close to the desired idle under the various engines loads with the engine idling.

Desired Idle - Range 0-3187 RPM: The VCM commands the desired IAC. The VCM compensates for various engine loads in order to maintain the desired idle speed.

Start Up ECT - Range -40°-215°C (-40°-419° F): When the engine is started, the VCM records the engine coolant temperature. The VCM uses the recorded temperature in order to calculate the time to a Closed Loop.

ECT - Range -40°-215°C (-40°-419°F): The Engine Coolant Temperature (ECT) sensor is mounted in the intake the intake manifold. The ECT sends the engine temperature information to the VCM. The VCM supplies 5 volts to the ECT sensor circuit. The sensor is a thermistor which changes the internal resistance as the temperature changes. When the sensor is cold meaning the internal resistance is high, the VCM monitors a high voltage signal. The VCM interprets the high voltage signal as a cold engine. As the sensor warms meaning the internal resistance decreases, the voltage signal decreases. The VCM interprets the lower resistance as a warm engine.

ECT - Sensor - Range (0.0-5.0 Volts): The Engine Coolant Temperature (ECT) sensor is mounted in the intake the intake manifold. The ECT sends the engine temperature information to the VCM. The VCM supplies 5 volts to the ECT sensor circuit. The sensor is a thermistor which changes the internal resistance as the temperature changes. When the sensor is cold meaning the internal resistance is high, the VCM monitors a high voltage signal. The VCM interprets the high voltage signal as a cold engine. As the sensor warms meaning the internal resistance decreases, the voltage signal decreases. The VCM interprets the lower resistance as a warm engine.

Startup IAT - Range (-40°-151°C): The VCM converts the resistance of the Intake Air Temperature (IAT) sensor to degrees. The VCM uses the intake air temperature in order to adjust the fuel delivery and the spark timing according to the incoming air density.

IAT - Range (-40°-151°C): The VCM converts the resistance of the Intake Air Temperature (IAT) sensor to degrees. The VCM uses the intake air temperature in order to adjust the fuel delivery and the spark timing according to the incoming air density.

Intake Air Temperature (IAT) Sensor - (0.0-5.0 Volts): The VCM converts the resistance of the Intake Air Temperature (IAT) sensor to degrees. The VCM uses the intake air temperature in order to adjust the fuel delivery and the spark timing according to the incoming air density.

Air Fuel Ratio - Range (0.0:1-25.5:1): The air to fuel ratio is based on the Oxygen sensor (HO2S) inputs. The VCM uses the fuel trim to adjust the fueling in order to attempt to maintain an air fuel ratio of 14.7:1. A lower number indicates a richer air fuel mixture. A higher number indicates a leaner mixture.

IAC Position - Range (0-255) Counts: The scan tool displays in counts the Idle Air Control (IAC) pintle position commanded from the VCM. The greater the number of counts, the greater the command idle speed (air passages opened) is. The idle air control should respond fairly quickly to changes in the engine load in order to maintain the desired idle RPM.

Desired IAC - Range (0-255) Counts: The desired IAC indicates the desired IAC position.

Throttle Position (TP) Sensor - Range (0.0-5.0 Volts): The VCM uses the Throttle Position in order to determine the amount of throttle demanded by the operator of the vehicle. The TP sensor reads between 0.36-0.96 volts at idle to above 4.0 volts at Wide Open Throttle (WOT).

TP Angle - Range (0-100%): The VCM computes the TP Angle from the TP signal voltage input. The TP Angle should read 0% at idle. AT 0 %, the TP voltage will read below 0.90 volts. The TP Angle should read 100% at Wide Open Throttle.

Manifold Absolute Pressure (MAP) - Range (10 kPa-104 kPa): The Manifold Absolute Pressure (MAP) sensor measures the change in the intake manifold pressure from the engine load and the speed changes. As the intake manifold pressure increases, the air density in the intake manifold also increases. Additional fuel is required.

Manifold Absolute Pressure (MAP) Sensor - Range (0.0-5.0 Volts): The MAP sensor produces a low signal voltage when the manifold pressure is low. A low manifold pressure means a high vacuum. The MAP sensor produces a high signal voltage when the manifold pressure is high. A high manifold pressure means a low vacuum. With the ignition ON and the engine stopped, the manifold pressure equals the atmospheric pressure causing the signal voltage to be high. The VCM uses this information as an indication of the vehicle's altitude. This information is referred to as the BARO. Comparison of this BARO reading with a known good vehicle with the same sensor is a good way to check accuracy of a suspect sensor. The readings should read the same +0.4 volt.

Barometric Pressure (BARO) Sensor - Range (0 kPa-62 kPa): The VCM determines the displayed BARO reading from the MAP sensor at the ignition ON and the engine OFF and the WOT conditions. The BARO reading displayed represents the barometric pressure. The VCM uses the displayed BARO readings in order to compensate for the altitude differences.

Barometric Pressure (BARO) - Range (0.0-5.0 Volts): The BARO represents a measurement of the barometric air pressure. This measurement is determined by using the Manifold Air Pressure (MAP) sensor in order to determine the manifold vacuum. Since the barometric air pressure depends on the altitude, the measurement may vary from 100 kPa (sea level) to 60 kPa (14,000 ft.).

Ignition 1 - Range (0.0-25.5 Volts): The Ignition 1 indicates the condition of the ignition input to the VCM.

Engine Speed - Range 0-16384 RPM: The VCM computes the Engine Speed from the fuel control reference input. The speed should remain close to the desired idle under the various engines loads with the engine idling.

Long Term Fuel Trim FT Bn 1 - Percentage of Compensation Required: The Long Term Fuel Trim (FT) is derived from the short term fuel trim value. The VCM uses the Long Term Fuel Trim for the long-term correction of the fuel delivery. A value of 128 counts (0% indicates that the fuel delivery requires no compensation to maintain a 14.7:1 air to fuel ratio. A value below 128 counts means that the fuel system is too rich and the fuel delivery is being reduced, decreased injector pulse width. A value above 128 counts indicates that a lean condition exists. The VCM compensates by adding fuel, increased injector pulse width.

Long Term Fuel Trim FT Bn 1 - Range (0-255) Counts: The Long Term Fuel Trim (FT) is derived from the short term fuel trim value. The VCM uses the Long Term Fuel Trim for the long-term correction of the fuel delivery. A value of 128 counts (0% indicates that the fuel delivery requires no compensation to maintain a 14.7:1 air to fuel ratio. A value below 128 counts means that the fuel system is too rich and the fuel delivery is being reduced, decreased injector pulse width. A value above 128 counts indicates that a lean condition exists. The VCM compensates by adding fuel, increased injector pulse width.

Long Term Fuel Trim FT Bn 2 - Percentage of Compensation Required: The Long Term Fuel Trim (FT) is derived from the short term fuel trim value. The VCM uses the Long Term Fuel Trim for the long-term correction of the fuel delivery. A value of 128 counts (0% indicates that the fuel delivery requires no compensation to maintain a 14.7:1 air to fuel ratio. A value below 128 counts means that the fuel system is too rich and the fuel delivery is being reduced, decreased injector pulse width. A value above 128 counts indicates that a lean condition exists. The VCM compensates by adding fuel, increased injector pulse width.

Long Term Fuel Trim FT Bn 2 - Range (0-255) Counts: The Long Term Fuel Trim (FT) is derived from the short term fuel trim value. The VCM uses the Long Term Fuel Trim for the long-term correction of the fuel delivery. A value of 128 counts (0% indicates that the fuel delivery requires no compensation to maintain a 14.7:1 air to fuel ratio. A value below 128 counts means that the fuel system is too rich and the fuel delivery is being reduced, decreased injector pulse width. A value above 128 counts indicates that a lean condition exists. The VCM compensates by adding fuel, increased injector pulse width.

Short Term Fuel Trim FT Bn 1 - Percentage of Compensation Required: The short term fuel trim was formerly the fuel integrator. The short term fuel trim represents a short-term correction to the fuel delivery by the VCM in response to the amount of time the HO2S voltage spends above or below the 450 mV threshold. A HO2S voltage reading below 450 mV indicates a lean air to fuel mixture. If the HO2S voltage has mainly been below 450 mV threshold, the short term fuel trim increases in order to tell the VCM to add fuel. If the HO2S voltage stays mainly above the threshold, the VCM reduces the fuel delivery in order to compensate for the indicated rich condition.

Short Term Fuel Trim FT Bn 1 - Range (0-255) Counts: The short term fuel trim was formerly the fuel integrator. The short term fuel trim represents a short-term correction to the fuel delivery by the VCM in response to the amount of time the HO2S voltage spends above or below the 450 mV threshold. A HO2S voltage reading below 450 mV indicates a lean air to fuel mixture. If the HO2S voltage has mainly been below 450 mV threshold, the short term fuel trim increases in order to tell the VCM to add fuel. If the HO2S voltage stays mainly above the threshold, the VCM reduces the fuel delivery in order to compensate for the indicated rich condition.

Short Term Fuel Trim FT Bn 2 - Percentage of Compensation Required: The short term fuel trim was formerly the fuel integrator. The short term fuel trim represents a short-term correction to the fuel delivery by the VCM in response to the amount of time the HO2S voltage spends above or below the 450 mV threshold. A HO2S voltage reading below 450 mV indicates a lean air to fuel mixture. If the HO2S voltage has mainly been below 450 mV threshold, the short term fuel trim increases in order to tell the VCM to add fuel. If the HO2S voltage stays mainly above the threshold, the VCM reduces the fuel delivery in order to compensate for the indicated rich condition.

Short Term Fuel Trim FT Bn 2 - Range (0-255) Counts: The short term fuel trim was formerly the fuel integrator. The short term fuel trim represents a short-term correction to the fuel delivery by the VCM in response to the amount of time the HO2S voltage spends above or below the 450 mV threshold. A HO2S voltage reading below 450 mV indicates a lean air to fuel mixture. If the HO2S voltage has mainly been below 450 mV threshold, the short term fuel trim increases in order to tell the VCM to add fuel. If the HO2S voltage stays mainly above the threshold, the VCM reduces the fuel delivery in order to compensate for the indicated rich condition.

FT Cell Bank 1 - Range (0-22) Cell: The Fuel Trim Cell is dependent upon the engine speed and the MAP sensor readings. A plot of the RPM vs the MAP sensor readings. A plot of the RPM vs the MAP is broken into 22 cells. The Fuel Trim Cell indicates which cell is currently active.

FT Cell Bank 2 - Range (0-22) Cell: The Fuel Trim Cell is dependent upon the engine speed and the MAP sensor readings. A plot of the RPM vs the MAP sensor readings. A plot of the RPM vs the MAP is broken into 22 cells. The Fuel Trim Cell indicates which cell is currently active.

Knock (KS) Sensor Activity - Range (0-255) Counts: The Knock Sensor Activity indicates the amount of spark knock detected by the VCM.

Knock (KS) Sensor - Range (0.0-5.0 Volts): The Knock Sensor indicates the amount of engine knock detected in volts.

Spark - Range (-96° to -255°): The Spark Advance is a display of the spark advance calculation which the VCM is programming into the ignition system. The VCM computes the desired spark advance using data such as the engine temperature, the RPM, the load, the vehicle speed, and the operating mode.

Knock Retard - Range (0.0-90°): The KS Retard indicates the amount of spark advances being removed in order to diminish the spark knock.

CMP Retard - Degrees: The CMP Retard indicates the difference between the CMP sensor and the CKP sensor in degrees.

Engine Run Time - Range (0:00:00-18:12:15) Hours: Minutes: Seconds: The Engine Run Time is a measure of how long the engine has run during this ignition cycle. When the engine stops running, the timer resets to zero.

Engine Data 2

Engine Speed - Range 0-16384 RPM: The VCM computes the Engine Speed from the fuel control reference input. The speed should remain close to the desired idle under the various engines loads with the engine idling.

Desired Idle - Range 0-3187 RPM: The VCM commands the desired IAC. The VCM compensates for various engine loads in order to maintain the desired idle speed.

EVAP Duty Cycle - Range (0-100%): The EVAP Duty Cycle indicates the EGR duty cycle that the VCM is commanding.

EVAP Canister Purge- OFF/ON: The EVAP Canister Purge pulls a small vacuum on the entire evaporative emission system. The scan tool displays if the EVAP Canister Purge Solenoid Valve is currently Off or On. When the scan tool displays ON, the small vacuum is being applied.

Air Fuel Ratio - Range (0.0:1-25.5:1): The Air to Fuel Ratio indicates the calculates Air to Fuel ratio that the VCM is commanding.

EGR Duty Cycle - (0%-100%): The EGR Duty Cycle determines a percentage of time the valve is being opened and closed.

Actual EGR Position - Range (0-100%): The Actual EGR Position indicates the actual EGR position in a percentage.

Desired EGR Position - Range (0-199.9%): The Desired EGR Position indicates the desired EGR position in a percentage.

EGR Sensor - Range (0.00-5.00 Volts): The EGR Sensor indicates the actual EGR position in voltage.

Air Fuel Ratio - Range (0.0:1-25.5:1): The Air to Fuel Ratio indicates the calculates Air to Fuel ratio that the VCM is commanding.

Ignition 1 - Range (0.0-25.5 Volts): The Ignition 1 indicates the condition of the ignition input to the VCM.

IAC Position - Range (0-255) Counts: The scan tool displays in counts the Idle Air Control (IAC) pintle position commanded from the VCM. The greater the number of counts, the greater the command idle speed (air passages opened) is. The idle air control should respond fairly quickly to changes in the engine load in order to maintain the desired idle RPM.

Desired IAC - Range (0-255) Counts: The desired IAC indicates the desired IAC position.

ECT - Range -40°-215°C (-40°-419°F): The Engine Coolant Temperature (ECT) sensor is mounted in the intake the intake manifold. The ECT sends the engine temperature information to the VCM. The VCM supplies 5 volts to the ECT sensor circuit. The sensor is a thermistor which changes the internal resistance as the temperature changes. When the sensor is cold meaning the internal resistance is high, the VCM monitors a high voltage signal. The VCM interprets the high voltage signal as a cold engine. As the sensor warms meaning the internal resistance decreases, the voltage signal decreases. The VCM interprets the lower resistance as a warm engine.

Start Up ECT - Range -40°-215°C (-40°-419°F): When the engine is started, the VCM records the engine coolant temperature. The VCM uses the recorded temperature in order to calculate the time to a Closed Loop.

IAT - Range (-40°-151°C): The VCM converts the resistance of the Intake Air Temperature (IAT) sensor to degrees. The VCM uses the intake air temperature in order to adjust the fuel delivery and the spark timing according to the incoming air density.

CMP Retard - Degrees: The CMP Retard indicates the difference between the CMP sensor and the CKP sensor in degrees.

Spark Control - Range (Advance/Retard): The Spark Control indicates if the VCM is commanding the spark advance or the spark retard.

Power Enrichment - Range (Yes/No): The Power Enrichment indicates if the Power Enrichment mode is active

Brake Switch - Range (Open/Closed): The Brake Switch indicates the status of the brake switch.

TR Switch: The Trans. Range indicates the current drive gear

A/B/C Range - Range (On/Off): The A/B/C Range indicates the current state of the transmission range switch.

Vehicle Speed- km/h - Range (0-255): The MPH - km/h indicates in MPH and in km/h how fast the drive wheels are turning.

Decel Fuel Mode - Range (Yes/No): The Decel Fuel Mode indicates if the VCM is in a Decel Fuel Mode.

1-2 Solenoid (Off/On): The scan tool will determine the status of the electronic solenoids in the automatic transmission. By determining the status of the solenoids, the correct gear state can also be determined.

2-3 Solenoid (Off/On): The scan tool will determine the status of the electronic solenoids in the automatic transmission. By determining the status of the solenoids, the correct gear state can also be determined.

3-2 Downshift Solenoid (Off/On): The scan tool will determine the status of the electronic solenoids in the automatic transmission. By determining the status of the solenoids, the correct gear state can also be determined.

TCC Enable - Range (Yes/No): The TCC Enable indicates the status of the TCC enable output.

TCC Duty Cycle- Range (0%-100%): The TCC Duty Cycle indicates the how often the vehicle is reaching a TCC lockup.

TCC Slip Speed - RPM: The TCC Slip Speed will be displayed on the scan tool based on the RPM of the engine and the amount of slip in a lockup condition.

Cruise Mode - Range (Yes/No): The Cruise Mode indicates if the driver has requested the cruise control.

Engine Run Time - Range (0:00:00-18:12:15) Hours: Minutes: Seconds: The Engine Run Time is a measure of how long the engine has run during this ignition cycle. When the engine stops running, the timer resets to zero.

Engine Data 3

Engine Speed - Range 0-16384 RPM: The VCM computes the Engine Speed from the fuel control reference input. The speed should remain close to the desired idle under the various engines loads with the engine idling.

Desired Idle - Range 0-3187 RPM: The VCM commands the desired IAC. The VCM compensates for various engine loads in order to maintain the desired idle speed.

IAC Position - Range (0-255) Counts: The scan tool displays in counts the Idle Air Control (IAC) pintle position commanded from the VCM. The greater the number of counts, the greater the command idle speed (air passages opened) is. The idle air control should respond fairly quickly to changes in the engine load in order to maintain the desired idle RPM.

Desired IAC - Range (0-255) Counts: The desired IAC indicates the desired IAC position.

Inj. PWM Avg. Bank 1 - Range (0-499 ms): The Inj. Avg. Bank 1 indicates the injector on time that the VCM is commanding.

Inj. PWM Avg. Bank 2 - Range (0-499 ms): The Inj. Avg. Bank 2 indicates the injector on time that the VCM is commanding.

Engine Load - Range (0-100%): The Engine Load indicates the engine load based on the Manifold Absolute Pressure. The higher the percentage, the greater the load the engine is under.

MAF Frequency (Hertz): The VCM converts the Mass Air Flow sensor input signal into grams per second or hertz. The MAF indicates the amount of air entering the engine.

MAF - Range 0-512 g/s: The VCM converts the Mass Air Flow sensor input signal into grams per second. The MAF indicates the amount of air entering the engine.

Throttle Position (TP) Sensor - Range (0.0-5.0 Volts): The VCM uses the Throttle Position in order to determine the amount of throttle demanded by the operator of the vehicle. The TP sensor reads between 0.36-0.96 volts at idle to above 4.0 volts at Wide Open Throttle (WOT).

TP Angle - Range (0-100%): The VCM computes the TP Angle from the TP signal voltage input. The TP Angle should read 0% at idle. AT 0 %, the TP voltage will read below 0.90 volts. The TP Angle should read 100% at Wide Open Throttle.

Manifold Absolute Pressure (MAP) - Range (10 kPa-104 kPa): The Manifold Absolute Pressure (MAP) sensor measures the change in the intake manifold pressure from the engine load and the speed changes. As the intake manifold pressure increases, the air density in the intake manifold also increases. Additional fuel is required.

Manifold Absolute Pressure (MAP) Sensor - Range (0.0-5.0 Volts): The MAP sensor produces a low signal voltage when the manifold pressure is low. A low manifold pressure means a high vacuum. The MAP sensor produces a high signal voltage when the manifold pressure is high. A high manifold pressure means a low vacuum. With the ignition ON and the engine stopped, the manifold pressure equals the atmospheric pressure causing the signal voltage to be high. The VCM uses this information as an indication of the vehicle's altitude. This information is referred to as the BARO. Comparison of this BARO reading with a known good vehicle with the same sensor is a good way to check accuracy of a suspect sensor. The readings should read the same +0.4 volt.

Barometric Pressure (BARO) Sensor - Range (0 kPa-62 kPa): The VCM determines the displayed BARO reading from the MAP sensor at the ignition ON and the engine OFF and the WOT conditions. The BARO reading displayed represents the barometric pressure. The VCM uses the displayed BARO readings in order to compensate for the altitude differences.

Barometric Pressure (BARO) - Range (0.0-5.0 Volts): The BARO represents a measurement of the barometric air pressure. This measurement is determined by using the Manifold Air Pressure (MAP) sensor in order to determine the manifold vacuum. Since the barometric air pressure depends on the altitude, the measurement may vary from 100 kPa (sea level) to 60 kPa (14,000 ft.).

EVAP Duty Cycle - Range (0-100%): The EVAP Duty Cycle indicates the EGR duty cycle that the VCM is commanding.

EGR Duty Cycle - (0%-100%): The EGR Duty Cycle determines a percentage of time the valve is being opened and closed.

Actual EGR Position - Range (0-100%): The Actual EGR Position indicates the actual EGR position in a percentage.

Desired EGR Position - Range (0-199.9%): The Desired EGR Position indicates the desired EGR position in a percentage.

EGR Sensor - Range (0.00-5.00 Volts): The EGR Sensor indicates the actual EGR position in voltage.

CMP Retard - Degrees: The CMP Retard indicates the difference between the CMP sensor and the CKP sensor in degrees.

A/C Request - Range (Yes/No): The A/C Request On indicates if the driver has requested the A/C.

A/C Relay - Range (Yes/No): The A/C Relay indicates the state of the A/C relay control circuit.

Engine Run Time - Range (0:00:00-18:12:15) Hours: Minutes: Seconds: The Engine Run Time is a measure of how long the engine has run during this ignition cycle. When the engine stops running, the timer resets to zero.

HO2S Data 4.3L/5.0L

Engine Speed - Range 0-16384 RPM: The VCM computes the Engine Speed from the fuel control reference input. The speed should remain close to the desired idle under the various engines loads with the engine idling.

Desired Idle - Range 0-3187 RPM: The VCM commands the desired IAC. The VCM compensates for various engine loads in order to maintain the desired idle speed.

Pre HO2S (Not Ready/Ready): The scan too will display the current state of the HO2S system.

Post HO2S (Not Ready/Ready): The scan too will display the current state of the HO2S system.

HO2S BN 1 Sen. 1 - Range (0-1107 mV): The HO2S BN 1 Sen. 1 indicates the activity of the HO2S (Bank 1 Sensor 1).

HO2S BN 1 Sen. 2 - Range (0-1107 mV): The HO2S BN 1 Sen. 2 indicates the activity of the HO2S (Bank 1 Sensor 2).

HO2S BN 2 Sen. 1 - Range (0-1107 mV): The HO2S BN 2 Sen. 1 indicates the activity of the HO2S (Bank 2 Sensor 1).

HO2S BN 1 Sen. 3 - Range (0-1107 mV): The HO2S BN 1 Sen. 3 indicates the activity of the HO2S (Bank 1 Sensor 3).

Air/Fuel Ratio - Range (0.0:1-25.5:1): The Air/Fuel Ratio indicates the calculated air to fuel ratio that the VCM is commanding.

HO2S Xcounts Bn 1 - Range (0-255): The HO2S Xcounts Bn 1 indicates the number of times that the HO2S (Bank 1 Sensor 1) crosses a threshold.

HO2S Xcounts Bn 2 - Range (0-255): The HO2S Xcounts Bn indicates the number of times that the HO2S (Bank 2 Sensor 1) crosses a threshold.

Rich/Lean Bn 1 - (Rich/Lean): The Rich/Lean Bn 1 indicates the condition of the exhaust gases in bank 1.

Rich/Lean Bn 2 - (Rich/Lean): The Rich/Lean Bn 2 indicates the condition of the exhaust gases in bank 2.

Loop Status - Range (Open/Close): The Loop Status indicates what mode of operation the VCM is in.

CL Since Restart - Range (Yes/No): The CL Since Restart indicates if the system has gone into a Closed Loop operation since the driver started the engine.

IAC Position - Range (0-255) Counts: The scan tool displays in counts the Idle Air Control (IAC) pintle position commanded from the VCM. The greater the number of counts, the greater the command idle speed (air passages opened) is. The idle air control should respond fairly quickly to changes in the engine load in order to maintain the desired idle RPM.

Desired IAC - Range (0-255) Counts: The desired IAC indicates the desired IAC position.

MAF - Range 0-512 g/s: The VCM converts the Mass Air Flow sensor input signal into grams per second. The MAF indicates the amount of air entering the engine.

Long Term Fuel Trim FT Bn 1 - Percentage of Compensation Required: The Long Term Fuel Trim (FT) is derived from the short term fuel trim value. The VCM uses the Long Term Fuel Trim for the long-term correction of the fuel delivery. A value of 128 counts (0% indicates that the fuel delivery requires no compensation to maintain a 14.7:1 air to fuel ratio. A value below 128 counts means that the fuel system is too rich and the fuel delivery is being reduced, decreased injector pulse width. A value above 128 counts indicates that a lean condition exists. The VCM compensates by adding fuel, increased injector pulse width.

Long Term Fuel Trim FT Bn 1 - Range (0-255) Counts: The Long Term Fuel Trim (FT) is derived from the short term fuel trim value. The VCM uses the Long Term Fuel Trim for the long-term correction of the fuel delivery. A value of 128 counts (0% indicates that the fuel delivery requires no compensation to maintain a 14.7:1 air to fuel ratio. A value below 128 counts means that the fuel system is too rich and the fuel delivery is being reduced, decreased injector pulse width. A value above 128 counts indicates that a lean condition exists. The VCM compensates by adding fuel, increased injector pulse width.

Long Term Fuel Trim FT Bn 2 - Percentage of Compensation Required: The Long Term Fuel Trim (FT) is derived from the short term fuel trim value. The VCM uses the Long Term Fuel Trim for the long-term correction of the fuel delivery. A value of 128 counts (0% indicates that the fuel delivery requires no compensation to maintain a 14.7:1 air to fuel ratio. A value below 128 counts means that the fuel system is too rich and the fuel delivery is being reduced, decreased injector pulse width. A value above 128 counts indicates that a lean condition exists. The VCM compensates by adding fuel, increased injector pulse width.

Long Term Fuel Trim FT Bn 2 - Range (0-255) Counts: The Long Term Fuel Trim (FT) is derived from the short term fuel trim value. The VCM uses the Long Term Fuel Trim for the long-term correction of the fuel delivery. A value of 128 counts (0% indicates that the fuel delivery requires no compensation to maintain a 14.7:1 air to fuel ratio. A value below 128 counts means that the fuel system is too rich and the fuel delivery is being reduced, decreased injector pulse width. A value above 128 counts indicates that a lean condition exists. The VCM compensates by adding fuel, increased injector pulse width.

Short Term Fuel Trim FT Bn 1 - Percentage of Compensation Required: The short term fuel trim was formerly the fuel integrator. The short term fuel trim represents a short-term correction to the fuel delivery by the VCM in response to the amount of time the HO2S voltage spends above or below the 450 mV threshold. A HO2S voltage reading below 450 mV indicates a lean air to fuel mixture. If the HO2S voltage has mainly been below 450 mV threshold, the short term fuel trim increases in order to tell the VCM to add fuel. If the HO2S voltage stays mainly above the threshold, the VCM reduces the fuel delivery in order to compensate for the indicated rich condition.

Short Term Fuel Trim FT Bn 1 - Range (0-255): The short term fuel trim was formerly the fuel integrator. The short term fuel trim represents a short-term correction to the fuel delivery by the VCM in response to the amount of time the HO2S voltage spends above or below the 450 mV threshold. A HO2S voltage reading below 450 mV indicates a lean air to fuel mixture. If the HO2S voltage has mainly been below 450 mV threshold, the short term fuel trim increases in order to tell the VCM to add fuel. If the HO2S voltage stays mainly above the threshold, the VCM reduces the fuel delivery in order to compensate for the indicated rich condition.

Short Term Fuel Trim FT Bn 2 - Range (0-255): The short term fuel trim was formerly the fuel integrator. The short term fuel trim represents a short-term correction to the fuel delivery by the VCM in response to the amount of time the HO2S voltage spends above or below the 450 mV threshold. A HO2S voltage reading below 450 mV indicates a lean air to fuel mixture. If the HO2S voltage has mainly been below 450 mV threshold, the short term fuel trim increases in order to tell the VCM to add fuel. If the HO2S voltage stays mainly above the threshold, the VCM reduces the fuel delivery in order to compensate for the indicated rich condition.

FT Cell Bank 1 - Range (0-22) Cell: The Fuel Trim Cell is dependent upon the engine speed and the MAP sensor readings. A plot of the RPM vs the MAP sensor readings. A plot of the RPM vs the MAP is broken into 22 cells. The Fuel Trim Cell indicates which cell is currently active.

FT Cell Bank 2 - Range (0-22) Cell: The Fuel Trim Cell is dependent upon the engine speed and the MAP sensor readings. A plot of the RPM vs the MAP sensor readings. A plot of the RPM vs the MAP is broken into 22 cells. The Fuel Trim Cell indicates which cell is currently active.

ECT - Range -40°-215°C (-40°-419°F): The Engine Coolant Temperature (ECT) sensor is mounted in the intake the intake manifold. The ECT sends the engine temperature information to the VCM. The VCM supplies 5 volts to the ECT sensor circuit. The sensor is a thermistor which changes the internal resistance as the temperature changes. When the sensor is cold meaning the internal resistance is high, the VCM monitors a high voltage signal. The VCM interprets the high voltage signal as a cold engine. As the sensor warms meaning the internal resistance decreases, the voltage signal decreases. The VCM interprets the lower resistance as a warm engine.

Start Up ECT - Range -40°-215°C (-40°-419°F): When the engine is started, the VCM records the engine coolant temperature. The VCM uses the recorded temperature in order to calculate the time to a Closed Loop.

Ignition 1 - Range (0.0-25.5 Volts): The Ignition 1 indicates the condition of the ignition input to the VCM.

Engine Run Time - Range (0:00:00-18:12:15) Hours: Minutes: Seconds: The Engine Run Time is a measure of how long the engine has run during this ignition cycle. When the engine stops running, the timer resets to zero.

HO2S Data 5.7L/7.4L

Engine Speed - Range 0-16384 RPM: The VCM computes the Engine Speed from the fuel control reference input. The speed should remain close to the desired idle under the various engines loads with the engine idling.

Desired Idle - Range 0-3187 RPM: The VCM commands the desired IAC. The VCM compensates for various engine loads in order to maintain the desired idle speed.

Pre HO2S (Not Ready/Ready): The scan too will display the current state of the HO2S system.

Post HO2S (Not Ready/Ready): The scan too will display the current state of the HO2S system.

HO2S BN 1 Sen. 1 - Range (0-1107 mV): The HO2S BN 1 Sen. 1 indicates the activity of the HO2S (Bank 1 Sensor 1).

HO2S BN 1 Sen. 2 - Range (0-1107 mV): The HO2S BN 1 Sen. 2 indicates the activity of the HO2S (Bank 1 Sensor 2).

HO2S BN 2 Sen. 1 - Range (0-1107 mV): The HO2S BN 2 Sen. 1 indicates the activity of the HO2S (Bank 2 Sensor 1).

HO2S BN 2 Sen. 2 - Range (0-1107 mV): The HO2S BN 1 Sen. 3 indicates the activity of the HO2S (Bank 1 Sensor 3).

Loop Status - Range (Open/Close): The Loop Status indicates what mode of operation the VCM is in.

HO2S Xcounts Bn 1 - Range (0-255): The HO2S Xcounts Bn 1 indicates the number of times that the HO2S (Bank 1 Sensor 1) crosses a threshold.

HO2S Xcounts Bn 2 - Range (0-255): The HO2S Xcounts Bn indicates the number of times that the HO2S (Bank 2 Sensor 1) crosses a threshold.

Rich/Lean Bn 1 - (Rich/Lean): The Rich/Lean Bn 1 indicates the condition of the exhaust gases in bank 1.

Rich/Lean Bn 2 - (Rich/Lean): The Rich/Lean Bn 2 indicates the condition of the exhaust gases in bank 2.

CL Since Restart - Range (Yes/No): The CL Since Restart indicates if the system has gone into a Closed Loop operation since the driver started the engine.

IAC Position - Range (0-255) Counts: The scan tool displays in counts the Idle Air Control (IAC) pintle position commanded from the VCM. The greater the number of counts, the greater the command idle speed (air passages opened) is. The idle air control should respond fairly quickly to changes in the engine load in order to maintain the desired idle RPM.

Desired IAC - Range (0-255) Counts: The desired IAC indicates the desired IAC position.

ECT - Range -40°-215°C (-40°-419°F): The Engine Coolant Temperature (ECT) sensor is mounted in the intake the intake manifold. The ECT sends the engine temperature information to the VCM. The VCM supplies 5 volts to the ECT sensor circuit. The sensor is a thermistor which changes the internal resistance as the temperature changes. When the sensor is cold meaning the internal resistance is high, the VCM monitors a high voltage signal. The VCM interprets the high voltage signal as a cold engine. As the sensor warms meaning the internal resistance decreases, the voltage signal decreases. The VCM interprets the lower resistance as a warm engine.

Start Up ECT - Range -40°-215°C (-40°-419°F): When the engine is started, the VCM records the engine coolant temperature. The VCM uses the recorded temperature in order to calculate the time to a Closed Loop.

MAF - Range 0-512 g/s: The VCM converts the Mass Air Flow sensor input signal into grams per second. The MAF indicates the amount of air entering the engine.

Long Term Fuel Trim FT Bn 1 - Percentage of Compensation Required: The Long Term Fuel Trim (FT) is derived from the short term fuel trim value. The VCM uses the Long Term Fuel Trim for the long-term correction of the fuel delivery. A value of 128 counts (0% indicates that the fuel delivery requires no compensation to maintain a 14.7:1 air to fuel ratio. A value below 128 counts means that the fuel system is too rich and the fuel delivery is being reduced, decreased injector pulse width. A value above 128 counts indicates that a lean condition exists. The VCM compensates by adding fuel, increased injector pulse width.

Long Term Fuel Trim FT Bn 1 - Range (0-255) Counts: The Long Term Fuel Trim (FT) is derived from the short term fuel trim value. The VCM uses the Long Term Fuel Trim for the long-term correction of the fuel delivery. A value of 128 counts (0% indicates that the fuel delivery requires no compensation to maintain a 14.7:1 air to fuel ratio. A value below 128 counts means that the fuel system is too rich and the fuel delivery is being reduced, decreased injector pulse width. A value above 128 counts indicates that a lean condition exists. The VCM compensates by adding fuel, increased injector pulse width.

Long Term Fuel Trim FT Bn 2 - Percentage of Compensation Required: The Long Term Fuel Trim (FT) is derived from the short term fuel trim value. The VCM uses the Long Term Fuel Trim for the long-term correction of the fuel delivery. A value of 128 counts (0% indicates that the fuel delivery requires no compensation to maintain a 14.7:1 air to fuel ratio. A value below 128 counts means that the fuel system is too rich and the fuel delivery is being reduced, decreased injector pulse width. A value above 128 counts indicates that a lean condition exists. The VCM compensates by adding fuel, increased injector pulse width.

Long Term Fuel Trim FT Bn 2 - Range (0-255) Counts: The Long Term Fuel Trim (FT) is derived from the short term fuel trim value. The VCM uses the Long Term Fuel Trim for the long-term correction of the fuel delivery. A value of 128 counts (0% indicates that the fuel delivery requires no compensation to maintain a 14.7:1 air to fuel ratio. A value below 128 counts means that the fuel system is too rich and the fuel delivery is being reduced, decreased injector pulse width. A value above 128 counts indicates that a lean condition exists. The VCM compensates by adding fuel, increased injector pulse width.

Short Term Fuel Trim FT Bn 1 - Percentage of Compensation Required: The short term fuel trim was formerly the fuel integrator. The short term fuel trim represents a short-term correction to the fuel delivery by the VCM in response to the amount of time the HO2S voltage spends above or below the 450 mV threshold. A HO2S voltage reading below 450 mV indicates a lean air to fuel mixture. If the HO2S voltage has mainly been below 450 mV threshold, the short term fuel trim increases in order to tell the VCM to add fuel. If the HO2S voltage stays mainly above the threshold, the VCM reduces the fuel delivery in order to compensate for the indicated rich condition.

Short Term Fuel Trim FT Bn 1 - Range (0-255): The short term fuel trim was formerly the fuel integrator. The short term fuel trim represents a short-term correction to the fuel delivery by the VCM in response to the amount of time the HO2S voltage spends above or below the 450 mV threshold. A HO2S voltage reading below 450 mV indicates a lean air to fuel mixture. If the HO2S voltage has mainly been below 450 mV threshold, the short term fuel trim increases in order to tell the VCM to add fuel. If the HO2S voltage stays mainly above the threshold, the VCM reduces the fuel delivery in order to compensate for the indicated rich condition.

Short Term Fuel Trim FT Bn 2 - Range (0-255): The short term fuel trim was formerly the fuel integrator. The short term fuel trim represents a short-term correction to the fuel delivery by the VCM in response to the amount of time the HO2S voltage spends above or below the 450 mV threshold. A HO2S voltage reading below 450 mV indicates a lean air to fuel mixture. If the HO2S voltage has mainly been below 450 mV threshold, the short term fuel trim increases in order to tell the VCM to add fuel. If the HO2S voltage stays mainly above the threshold, the VCM reduces the fuel delivery in order to compensate for the indicated rich condition.

FT Cell Bank 1 - Range (0-22) Cell: The Fuel Trim Cell is dependent upon the engine speed and the MAP sensor readings. A plot of the RPM vs the MAP sensor readings. A plot of the RPM vs the MAP is broken into 22 cells. The Fuel Trim Cell indicates which cell is currently active.

FT Cell Bank 2 - Range (0-22) Cell: The Fuel Trim Cell is dependent upon the engine speed and the MAP sensor readings. A plot of the RPM vs the MAP sensor readings. A plot of the RPM vs the MAP is broken into 22 cells. The Fuel Trim Cell indicates which cell is currently active.

Ignition 1 - Range (0.0-25.5 Volts): The Ignition 1 indicates the condition of the ignition input to the VCM.

Air/Fuel Ratio - Range (0.0:1-25.5:1): The Air/Fuel Ratio indicates the calculated air to fuel ratio that the VCM is commanding.

Engine Run Time - Range (0:00:00-18:12:15) Hours: Minutes: Seconds: The Engine Run Time is a measure of how long the engine has run during this ignition cycle. When the engine stops running, the timer resets to zero.

Misfire Data 4.3L

Engine Speed - Range 0-16384 RPM: The VCM computes the Engine Speed from the fuel control reference input. The speed should remain close to the desired idle under the various engines loads with the engine idling.

Desired Idle - Range 0-3187 RPM: The VCM commands the desired IAC. The VCM compensates for various engine loads in order to maintain the desired idle speed.

Misfire Current Cyl. #1: The scan tool will display the number of current cylinder misfires.

Misfire Current Cyl. #2: The scan tool will display the number of current cylinder misfires.

Misfire Current Cyl. #3: The scan tool will display the number of current cylinder misfires.

Misfire Current Cyl. #4: The scan tool will display the number of current cylinder misfires.

Misfire Current Cyl. #5: The scan tool will display the number of current cylinder misfires.

Misfire Current Cyl. #6: The scan tool will display the number of current cylinder misfires.

Engine Speed - Range 0-16384 RPM: The VCM computes the Engine Speed from the fuel control reference input. The speed should remain close to the desired idle under the various engines loads with the engine idling.

Desired Idle - Range 0-3187 RPM: The VCM commands the desired IAC. The VCM compensates for various engine loads in order to maintain the desired idle speed.

Misfire History Cyl. #1: The scan tool will display the number of history cylinder misfires.

Misfire History Cyl. #2: The scan tool will display the number of history cylinder misfires.

Misfire History Cyl. #3: The scan tool will display the number of history cylinder misfires.

Misfire History Cyl. #4: The scan tool will display the number of history cylinder misfires.

Misfire History Cyl. #5: The scan tool will display the number of history cylinder misfires.

Misfire History Cyl. #6: The scan tool will display the number of history cylinder misfires.

IAC Position - Range (0-255) Counts: The scan tool displays in counts the Idle Air Control (IAC) pintle position commanded from the VCM. The greater the number of counts, the greater the command idle speed (air passages opened) is. The idle air control should respond fairly quickly to changes in the engine load in order to maintain the desired idle RPM.

Desired IAC - Range (0-255) Counts: The desired IAC indicates the desired IAC position.

Ignition 1 On - Range (Yes/No) : The Ignition 1 On indicates the condition of the ignition input to the VCM.

Rich/Lean Bn 1 - (Rich/Lean): The Rich/Lean Bn 1 indicates the condition of the exhaust gases in bank 1.

Rich/Lean Bn 2 - (Rich/Lean): The Rich/Lean Bn 2 indicates the condition of the exhaust gases in bank 2.

Brake Switch - Range (Open/Closed): The Brake Switch indicates the status of the brake switch.

Decel Fuel Mode - Range (Yes/No): The Decel Fuel Mode indicates if the VCM is in a Decel Fuel Mode.

Power Enrichment - Range (Yes/No): The Power Enrichment indicates if the Power Enrichment mode is active

TR Switch: The Trans. Range indicates the current drive gear

TCC Forced Off (No/Yes): The scan tool will display the status of the VCM.

TCC Enable - Range (Yes/No): The TCC Enable indicates the status of the TCC enable output.

Misfire Data 5.0L, 5.7L, 7.4L

Engine Speed - Range 0-16384 RPM: The VCM computes the Engine Speed from the fuel control reference input. The speed should remain close to the desired idle under the various engines loads with the engine idling.

Desired Idle - Range 0-3187 RPM: The VCM commands the desired IAC. The VCM compensates for various engine loads in order to maintain the desired idle speed.

Misfire Current Cyl. #1: The scan tool will display the number of current cylinder misfires.

Misfire Current Cyl. #2: The scan tool will display the number of current cylinder misfires.

Misfire Current Cyl. #3: The scan tool will display the number of current cylinder misfires.

Misfire Current Cyl. #4: The scan tool will display the number of current cylinder misfires.

Misfire Current Cyl. #5: The scan tool will display the number of current cylinder misfires.

Misfire Current Cyl. #6: The scan tool will display the number of current cylinder misfires.

Misfire Current Cyl. #7: The scan tool will display the number of current cylinder misfires.

Misfire Current Cyl. #8: The scan tool will display the number of current cylinder misfires.

Engine Speed - Range 0-16384 RPM: The VCM computes the Engine Speed from the fuel control reference input. The speed should remain close to the desired idle under the various engines loads with the engine idling.

Misfire History Cyl. #1: The scan tool will display the number of history cylinder misfires.

Misfire History Cyl. #2: The scan tool will display the number of history cylinder misfires.

Misfire History Cyl. #3: The scan tool will display the number of history cylinder misfires.

Misfire History Cyl. #4: The scan tool will display the number of history cylinder misfires.

Misfire History Cyl. #5: The scan tool will display the number of history cylinder misfires.

Misfire History Cyl. #6: The scan tool will display the number of history cylinder misfires.

Misfire History Cyl. #7: The scan tool will display the number of history cylinder misfires.

Misfire History Cyl. #8: The scan tool will display the number of history cylinder misfires.

IAC Position - Range (0-255) Counts: The scan tool displays in counts the Idle Air Control (IAC) pintle position commanded from the VCM. The greater the number of counts, the greater the command idle speed (air passages opened) is. The idle air control should respond fairly quickly to changes in the engine load in order to maintain the desired idle RPM.

Desired IAC - Range (0-255) Counts: The desired IAC indicates the desired IAC position.

Ignition 1 On - Range (Yes/No) : The Ignition 1 On indicates the condition of the ignition input to the VCM.

Rich/Lean Bn 1 - (Rich/Lean): The Rich/Lean Bn 1 indicates the condition of the exhaust gases in bank 1.

Rich/Lean Bn 2 - (Rich/Lean): The Rich/Lean Bn 2 indicates the condition of the exhaust gases in bank 2.

Brake Switch - Range (Open/Closed): The Brake Switch indicates the status of the brake switch.

Decel Fuel Mode - Range (Yes/No): The Decel Fuel Mode indicates if the VCM is in a Decel Fuel Mode.

Power Enrichment - Range (Yes/No): The Power Enrichment indicates if the Power Enrichment mode is active

TR Switch: The Trans. Range indicates the current drive gear

TCC Forced Off (No/Yes): The scan tool will display the status of the VCM.

TCC Enable - Range (Yes/No): The TCC Enable indicates the status of the TCC enable output.