Engine Data 1

Engine Speed--Range (0-16,384 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 Speed--Range (0-3,187 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 Position--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.

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.

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.

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.

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).

Barometric Pressure (BARO) Sensor-- Range (0-62 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.

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 Sensor--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.

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.

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.

Engine Load--Range (0-100%): The VCM determines the engine load based upon the engine speed and MAF sensor readings. Engine Load increases with any increase in RPM and/or airflow.

Engine Speed--Range 0-16,384 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.

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.

EVAP Duty Cycle--Range (0-100%): The scan tool indicates the EVAP duty cycle that the VCM is commanding. The EVAP duty cycle is a pulse modulated signal which is translated into a direct percentage of the maximum commandable state.

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.

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.

Ref. Pulse Occurred--Range (Yes/No): The scan tool will indicate a Yes for up to 1 second after a reference pulse has been detected by the CKP.

Valid Ref. Pulse Occurred--Range (Yes/No): The scan tool will indicate a Yes after 2 or more reference pulses have been detected by the CKP.

Knock (KS) Sensor--Range (0.0-5.0 Volts): The scan tool indicates the current knock sensor voltage.

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

Spark--Range (-96 Degrees to -255 Degrees): 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 degrees): The KS Retard indicates the amount of spark advance is the VCM removes in order to diminish spark knock.

CMP Retard--Range (0.0-90 degrees): The CAM Retard indicates the difference between the CMP sensor and the CKP sensor relationship

Spark Control--Range (Advance/Retard): The Spark Control indicates whether the VCM is advancing or retarding spark.

Loop Status--Range (Open/Close): The Loop Status indicates that the VCM is controlling fuel delivery according to HO2S input. During open loop, the VCM ignores the HO2S input and bases fuel delivery upon TP, engine coolant, and MAF sensor input.

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

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.

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

Air Fuel Ratio--Range (0.0:1-25.5:1): The scan tool indicates the VCM calculated air to fuel ratio. The typical air to fuel ratio is 14.7:1.

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 (0-16,384 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.

Desire Idle Speed--Range (0-3,187 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 Position--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 percent at idle. AT 0 percent, the TP voltage will read below 0.90 volts. The TP Angle should read 100% at Wide Open Throttle.

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 Sensor--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.

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.

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.

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).

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.

Engine Load--Range (0-100%): The VCM determines the engine load based upon the engine speed and MAF sensor readings. Engine Load increases with any increase in RPM and/or airflow.

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.

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.

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.

EVAP Duty Cycle--Range (0-100%): The scan tool indicates the EVAP duty cycle that the VCM is commanding. The EVAP duty cycle is a pulse modulated signal which is translated into a direct percentage of the maximum commandable state.

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.

EVAP Vent Solenoid--(Closed/Open): The scan tool will show the status of the EVAP Vent Solenoid.

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.

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 Closed Loop Since Restart indicates whether or not the vehicle has been in a closed loop state.

VTD Fuel Disable--Range (Active/Inactive): If the VCM has not received the correct password from the Passlock Module or Body Control Module (if equipped), the VCM will disable fuel to the fuel system. If this occurs, the scan tool will display Active.

VTD Auto Learn Timer--Range (Active/Inactive): The Auto Learn Timer will indicate if the Vehicle Theft Deterrent (VTD) system is in the learn mode and has not timed out (approx 10 minutes).

PCM/VCM in VTD Fail--Range (Yes/No): This will indicate when the VCM has received a good password from the Passlock Module or Body Control Module (if equipped), the vehicle has started, and a failure has occurred. The VCM will continue to enable fuel.

VTD Fuel Disable Until--Range (Yes/No): With the ignition ON and a VTD code stored, the scan tool will display Yes.

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

Ignition 1 On--Range (Yes/No): The Ignition 1 On indicates the presence of a valid ignition 1 signal. The normal ignition 1 voltage is approximately 13.8 volts, but may vary between 11-16 volts. The VCM monitors the ignition 1 voltage to compensate for low voltage operation of the injectors and to increase dwell time of the ignition timing signal to the distributor.

Ignition 1 Low--Range (Yes/No): The scan tool indicates whether a low ignition voltage has been detected. A low ignition 1 voltage may degrade ignition timing and injector operation. The normal ignition 1 voltage is approximately 13.8 volts, but may vary between 11-16 volts.

Ignition 1 High--Range (Yes/No): The scan tool indicates whether a high ignition voltage has been detected. An excessively high ignition 1 voltage could damage hardware. The normal ignition 1 voltage is approximately 13.8 volts, but may vary between 11-16 volts.

A/C Request--Range (Yes/No): The scan tool indicates the state of the A/C request input circuit. The VCM uses the A/C request signal in order to determine whether A/C compressor operation has been requested.

A/C Relay--Range (Yes/No): The scan tool indicates whether the A/C relay control circuit has been commanded ON.

A/C Evaporator Switch--Range (Open/Closed): The A/C Evaporator Switch is used to indicate to the VCM if the A/C clutch should be enabled or disabled. The switch is opened when the compressor is between approximately 22-45.5 psi.

A/C Sec. High Pres. Switch--Range (Open/Closed):  The switch notifies the VCM when the compressor pressure limit is approached. The switch closes at a high pressure value which is calibrated for specific platforms. The VCM monitors the secondary high pressure switch at least every 100 ms.

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.

1-2 Solenoid--Range (ON/OFF): The scan tool indicates whether the automatic transmission's shift solenoid is active.

2-3 Solenoid--Range (ON/OFF): The scan tool indicates whether the automatic transmission's shift solenoid is active.

3-2 Downshift Solenoid--Range (ON/OFF): The scan tool indicates whether the automatic transmission's shift solenoid is active.

TCC Duty Cycle--Range (0-100%): The scan tool indicates the amount that the VCM commands the TCC ON. The TCC solenoid is pulse modulated to provide a determined amount of pressure, which is translated into a percentage of the supply pressure. An open solenoid circuit would cause the duty cycle to be fixed at maximum.

Cruise--Range (Enable/Disable): The Cruise Mode indicates if the driver has requested the cruise control.

Decel Fuel Mode--Range (Active/Inactive): The scan tool indicates whether the vehicle is in fuel cutoff mode.

Mileage Since DTC Clear--Range (Km/Mi): The scan tool indicates the total distance the vehicle has traveled since the DTCs were cleared.

DTC Set this Ignition--Range (Yes/No): The scan tool indicates whether or not any DTC has set during the current ignition cycle.

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

Engine Speed--Range (0-16,384 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 Speed--Range (0-3,187 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 Position--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.

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.

Loop Status--Range (Open Loop/Closed Loop): The scan tool indicates whether the vehicle is in an open or closed loop state. The VCM uses HO2S information for determining fuel delivery during closed loop.

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

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.

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

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.

CL Since Restart--Range (Yes/No): The Closed Loop Since Restart indicates whether or not the vehicle has been in a closed loop state.

Air Fuel Ratio--Range (0.0:1-25.5:1): The scan tool indicates the VCM calculated air to fuel ratio. The typical air to fuel ratio is 14.7:1.

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.

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.

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.

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.

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.

Engine Load--Range (0-100%): The VCM determines the engine load based upon the engine speed and MAF sensor readings. Engine Load increases with any increase in RPM and/or airflow.

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.

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.

EVAP Duty Cycle--Range (0-100%): The scan tool indicates the EVAP duty cycle that the VCM is commanding. The EVAP duty cycle is a pulse modulated signal which is translated into a direct percentage of the maximum commandable state.

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.

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

Mileage Since DTC Clear--Range (Km/Mi): The scan tool indicates the total distance the vehicle has traveled since the DTCs were cleared.

DTC Set this Ignition--Range (Yes/No): The scan tool indicates whether or not any DTC has set during the current ignition cycle.

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.

EVAP Data (1998 Only)

Engine Speed--Range (0-16,384 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 Speed--Range (0-3,187 RPM): The VCM commands the desired IAC. The VCM compensates for various engine loads in order to maintain the desired idle speed.

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.

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.

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.

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.

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.

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).

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.

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.

EVAP Canister Purge--(ON/OFF): 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.

EVAP Duty Cycle--Range (0-100%): The scan tool indicates the EVAP duty cycle that the VCM is commanding. The EVAP duty cycle is a pulse modulated signal which is translated into a direct percentage of the maximum commandable state.

EVAP Vent Solenoid--(Closed/Open): The scan tool will show the status of the EVAP Vent Solenoid.

Fuel Tank Pressure--(-20-7 in H2O): The scan tool indicates the current fuel tank pressure that is converted by the VCM using the fuel tank pressure sensor signal voltage. As pressure decreases a greater vacuum is created.

Excess Vacuum Test--(Pass/Not R/F): The Excess Vacuum Test will fail if the fuel tank vacuum builds at an excessive rate during normal EVAP canister purge. A restricted vent valve or vent valve hoses will cause improper venting.

Weak Vacuum Test--(Pass/Not R/F): The Weak Vacuum Test only runs if the Loaded Canister Test does not pass. Insufficient vacuum buildup during normal purge operation with the vent valve closed will cause this test to fail.

Small Leak Test--(Pass/Not R/F): The Small Leak Test runs immediately after the Weak Vacuum Test. The EVAP system is closed and the fuel tank vacuum is monitored by the VCM. A high loss of vacuum rate will cause this test to fail. This test may run up to three times before reporting a failure.

Purge Leak Test--(Pass/Not R/F): The Purge Leak Test runs only after a cold start occurred during the current ignition and the Weak Vacuum Test did not fail. The VCM commands both the purge and vent valves closed. If a vacuum builds, then the restricted or inoperative vent valve will cause this test to fail.

Fuel Level--Range (0-100%): The scan tool indicates the current percentage of fuel tank occupancy. The float position changes the value of a variable resistor who's voltage the VCM converts to the displayed percentage.

Fuel Level Sensor--(0.0-2.9 volts): The scan tool will display the voltage coming from the Fuel Level Sensor which will vary from 0.39-2.9 volts.

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 Loop/Closed Loop): The scan tool indicates whether the vehicle is in an open or closed loop state. The VCM uses HO2S information for determining fuel delivery during closed loop.

Engine Load--Range (0-100%): The VCM determines the engine load based upon the engine speed and MAF sensor readings. Engine Load increases with any increase in RPM and/or airflow.

Fuel Trim Cell --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 Adjust Factor--Range (-90-90°): The knock sensor is a piezoelectric device which detects vibration due to spark knock. The VCM converts the knock sensor signal according to calibrated values; thus allowing the engine to operate at optimum spark advance with out knock to improve driveability and fuel economy.

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.