The Engine Scan Tool Data Definitions contains a brief description of all engine related parameters available on the scan tool. The list is in alphabetical order. A given parameter may appear in any one of the data lists. In some cases, the parameter may appear more than once or in more than one data list in order to group certain related parameters together.

A/C Off For WOT: The scan tool displays YES or NO. Indicates whether A/C is commanded OFF due to wide open throttle (WOT).

A/C Pressure Disable: The scan tool displays YES or NO. Indicates whether A/C is commanded OFF due to excessive or insufficient pressure.

A/C Relay Command: This parameter displays the commanded state of the air conditioning (A/C) clutch relay control circuit. The scan tool will display ON or OFF. ON indicates that the A/C clutch relay control circuit is being grounded by the control module, allowing voltage to the A/C compressor clutch. OFF indicates that the A/C clutch relay is not being commanded ON by the control module.

A/C Request Signal: This parameter displays the state of the air conditioning (A/C) request input to the control module from the heating, ventilation, and air conditioning (HVAC) controls. The scan tool will display Yes or No. Yes indicates that the control module is receiving a request from the HVAC system to ground the A/C clutch relay control circuit, engaging the A/C compressor clutch. No indicates that the control module is not receiving a request from the HVAC system to ground the A/C clutch relay control circuit.

Air Fuel Ratio: This parameter displays the ratio of air to fuel as calculated by the control module based on various sensor inputs. The scan tool will display a lower air fuel ratio when a richer air to fuel mixture is commanded. The scan tool will display a higher air fuel ratio when a leaner air to fuel mixture is commanded. In Closed Loop operation the air fuel ratio should normally be 14.2-14.7 to 1.

APP Indicated Angle: This parameter displays the angle of the accelerator pedal as calculated by the control module using the signals from the accelerator pedal position sensors. The APP indicated angle is a range of values indicating a low percentage when the accelerator pedal is not depressed to a high percentage when the accelerator pedal is fully depressed.

APP Sensor 1: This parameter displays the voltage signal sent to the control module from accelerator pedal position (APP) sensor 1 of the APP sensor assembly. APP sensor 1 is a range of values indicating a low voltage when the accelerator pedal is not depressed to a high voltage when the accelerator pedal is fully depressed.

APP Sensor 1 Circuit Status: This parameter displays the diagnostic state of the APP sensor 1 circuit. The scan tool will display OK or Fault. OK indicates that no circuit faults are detected during the current test. Fault indicates that a short or open circuit/component exists.

APP Sen. 1 and 2: This parameter displays the results of a control module test that compares the signals from the accelerator pedal position (APP) sensors 1 and 2 . The scan tool will display Agree or Disagree. Agree indicates that APP sensor 1 and APP sensor 2 voltages correspond to the same accelerator pedal position. Disagree indicates that APP sensor 1 and APP sensor 2 voltages correspond to different accelerator pedal positions.

APP Sensor 2: This parameter displays the voltage signal sent to the control module from accelerator pedal position (APP) sensor 2 of the APP sensor assembly. The APP sensor 2 is a range of values indicating a high voltage when the accelerator pedal is not depressed to a low voltage when the accelerator pedal is fully depressed.

APP Sensor 2 Circuit Status: This parameter displays the diagnostic state of the APP sensor 2 circuit. The scan tool will display OK or Fault. OK indicates that no circuit faults are detected during the current test. Fault indicates that a short or open circuit/component exists.

BARO: This parameter displays the barometric pressure as calculated by the control module using the signal from the sensor measured when the ignition is turned ON or with the engine running.

Catalytic Converter Protection Active: This parameter displays the state of the Catalytic Converter Protection mode.

CKP Active Counter: The crankshaft position (CKP) active counter displays whether the PCM is receiving the pulses from the CKP sensor.

CMP Active Counter: This parameter displays an incrementing counter when the control module receives a signal from the camshaft position (CMP) sensor.

CMP Sensor: This parameter displays the speed of the engine as calculated by the signal from the camshaft position (CMP) sensor.

Crank Request: This parameter displays whether the ignition switch has been cycled to the crank position requesting the control module to activate the starter relay.

Cruise Control Active: This parameter displays the status of the cruise control system as determined by the control module. The scan tool will display Yes when the cruise control system is in control of vehicle speed. The scan tool will display No when the cruise control system is not operating.

Cruise Disengage 1-8 History: The parameter displays the last 8 cruise control disengages in order from 1 to 8, with 8 being the most recent. There are about 33 possible causes for the cruise control to disengage.

Cruise On/Off Switch: This parameter displays the state of the cruise control on/off switch input to the control module.

Cruise Resume/Accel. Switch: This parameter displays the state of the cruise controls resume/accel switch position input to the control module.

Cycles of Misfire Data: The scan tool displays a range of 0-100. The powertrain control module (PCM) counts the number of misfire tests during 200 engine revolutions.

Decel. Fuel Cutoff: This parameter displays the status of the operating mode used to turn off the fuel injectors during certain deceleration conditions. When the can tool displays Active, the control module has turned off the fuel injectors. When the scan tool displays Inactive, the fuel system is operating normally.

Desired Idle Speed: This parameter displays the engine idle speed in RPM commanded by the control module. The control module compensates for various engine loads in order to maintain the desired engine RPM at idle. This parameter is not valid unless the engine is running.

EC Ignition Relay Feedback Signal: This parameter displays the voltage available at the EC ignition relay pin of the control module.

ECT Sensor: The powertrain control module (PCM) applies 5 volts to the engine coolant temperature (ECT) sensor circuit. The sensor is a thermistor which changes internal resistance as the engine temperature changes. When the sensor is cold, internal resistance high, the PCM senses a high signal voltage and interprets the voltage as a cold engine. As the sensor warms, internal resistance decreases, the voltage signal decreases and the PCM interprets the lower voltage as a warm engine.

Engine Load: This parameter displays the engine load in percent based on inputs to the control module from various engine sensors. The scan tool will display a low percentage when the engine is at idle with little or no load. The scan tool will display a high percentage when the engine is running at a high RPM under a heavy load.

Engine Off Time: This parameter displays the time elapsed since the engine was shut off.

Engine Oil Life Remaining: The PCM calculates engine oil life based upon the number of engine revolutions seen and operating conditions such as calculated oil temperature. Pressing the oil life monitor reset switch will return the displayed engine oil life to 100 percent.

Engine Oil Pressure Switch: This parameter displays OK or low.

Engine Run Time: This parameter displays the time elapsed since the engine was started. The scan tool will display the time in hours, minutes and seconds. The engine run time will reset to zero as soon as the engine stops running.

Engine Speed: The powertrain control module (PCM) computes engine speed from the ignition reference pulses. The engine speed should remain close to desired idle under various engine loads with the engine idling.

EVAP Fault History: This parameter displays the result of the EVAP System diagnostic. The scan tool displays NO FAULT, EXCESS VACUUM, PURGE VALVE LEAK, SMALL LEAK, NO TEST RESULT, or WEAK VACUUM. The EVAP Fault History indicates the status of EVAP system diagnostics performed by the PCM.

EVAP Purge Solenoid Command: This parameter displays the on-time or duty cycle of the evaporative emission (EVAP) purge solenoid commanded by the control module expressed as a percent. The scan tool will display a high percentage when the control module is commanding the EVAP purge solenoid to be open a large amount . The scan tool will display a low percentage when the control module is commanding the EVAP purge solenoid to be open a small amount. The scan tool will display 0 when the control module is commanding the EVAP purge solenoid closed.

EVAP Vent Solenoid Command: The scan tool displays Venting or Not Venting. The evaporative emission (EVAP) canister vent valve is normally open. The powertrain control module (PCM) commands the EVAP canister vent valve closed, during testing of the EVAP system.

FC Relay 1 Command: Indicates the commanded state of the FC Relay. The scan tool displays ON or OFF.

Fuel Tank Level Remaining: This parameter displays the amount of fuel remaining in the fuel tank as a percentage. The control module calculates this level using the signal from the sensor used to monitor the fuel level in the fuel tank. The scan tool will display a low reading when the fuel level in the tank is low or near empty. The scan tool will display a high reading when the fuel level in the tank is high or near full.

Fuel Tank Pressure Sensor: This parameter displays the voltage signal sent to the control module from the sensor used to monitor the pressure inside the fuel tank. The scan tool will display a low voltage when the pressure in the fuel tank is high. The scan tool will display a high voltage when the pressure in the fuel tank is low or in a vacuum.

Fuel Tank Pressure Sensor: The scan tool displays mm/Hg and in H2O vacuum or pressure.

Fuel Trim Cell: The powertrain control module (PCM) determines from the manifold absolute pressure (MAP) and RPM inputs which fuel trim cell to operate the engine in. The fuel trim cell displayed on the scan tool is the cell that the engine is operating under.

Fuel Trim Learn: This parameter indicates if the control module is adjusting long term fuel trim in response to the short term fuel trim. The scan tool displays Enabled or Disabled. When conditions are appropriate form enabling long term fuel trim corrections, the scan tool displays Enabled.

Gen F-Terminal Signal: Represents the field terminal input from the generator. The field PWM duty cycle indicates generator output level. A higher duty cycle indicates a higher generator output. The PCM uses the generator F terminal signal in order to adjust spark and idle air control (IAC) to compensate for variances in engine load caused by the generator.

Generator L-Terminal Signal: The scan tool displays Voltage/No Voltage.

HO2S 1: The scan tool displays a range of 0-1,106 mV.

HO2S 2: The scan tool displays a range of 0-1,106 mV.

HO2S 1 Heater: This parameter displays the current through the control module when the HO2S 1 heater is commanded ON by the control module. HO2S 1 Heater Current is a range of values indicating a low current when the heater circuit resistance is high to a high current when the heater circuit resistance is low.

HO2S 2 Heater: This parameter displays the current through the control module when the HO2S 2 heater is commanded ON by the control module. HO2S 2 Heater Current is a range of values indicating a low current when the heater circuit resistance is high to a high current when the heater circuit resistance is low.

IAT Sensor: The powertrain control module (PCM) converts the resistance of the intake air temperature (IAT) sensor to degrees. The PCM uses the IAT in order to adjust fuel delivery and spark timing according to incoming air density.

Initial Brake Apply Signal: This parameter displays the state of the brake pedal that is transmitted over the serial data circuit from the electronic brake control module (EBCM).

Ignition 1 Signal: This parameter displays the voltage measured at the ignition 1 circuit of the control module. Voltage is applied to the control module when the ignition switch is in the ignition 1 position.

Injector PWM: Indicates the base pulse width modulation (PWM) or ON time of the fuel injectors in milliseconds. When the engine load is increased, the injector pulse width will increase.

Knock Retard: Knock retard indicates the amount of spark the powertrain control module (PCM) removes from the spark advance in response to the signal from the knock sensors.

Long Term FT: The scan tool displays percentage. The powertrain control module (PCM) derives the long term fuel trim from the short term fuel trim value. The long term fuel trim represents a long term correction of fuel delivery. A value of 0 percent indicates that fuel delivery requires no compensation in order to maintain the PCM commanded air/fuel ratio. A negative value significantly below 0 percent indicates that the fuel system is rich and the PCM is reducing the fuel delivery. A positive value significantly more than 0  percent indicates that a lean condition exists and the PCM compensates by adding fuel. Fuel trim values at maximum authority indicates an excessively rich or lean system.

Long Term FT Avg.: This parameter is the average long term fuel trim for this bank as calculated by the control module. The scan tool will display a value more than 0 percent indicating that time is being added to the injector pulse width, increasing the amount of fuel to this bank of the engine. The scan tool will display a value of less than 0, indicating time is being subtracted from the injector pulse width, reducing the amount of fuel to this bank of the engine. A value of 0 percent indicates no compensation is required to operate the engine at the desired air/fuel ratio.

Loop Status: The scan tool displays Open or Closed. Closed Loop indicates that the powertrain control module (PCM) is controlling fuel delivery according to oxygen sensor voltage. In Open Loop, the PCM ignores the oxygen sensor voltage and bases the amount of fuel to be delivered on throttle position (TP) sensor, engine coolant temperature (ECT) sensor inputs only.

MAF Sensor: Mass air flow (MAF) is the MAF input frequency converted to grams of air per second. This indicates the amount of air entering the engine.

MAF Sensor: The mass air flow sensor input signal to the PCM is a frequency which varies from around 3,000 Hz at idle to above 7,000 Hz at wide open throttle (WOT). The PCM converts this frequency signal to grams per second to be displayed on the scan tool as MAF.

MAP Sensor: The manifold absolute pressure (MAP) sensor measures the absolute pressure in the intake manifold.

Medium Resolution Resync Counter: The medium resolution resync counter displays the number of times the PCM had to resync the crankshaft position (CKP) sensor.

MIL Command: This parameter displays the commanded state of the malfunction indicator lamp (MIL) control circuit. The malfunction indicator lamp should be on when the scan tool indicates the MIL Command is On. The malfunction indicator lamp should be off when the scan tool indicates the MIL Command is Off. The control module will command the MIL On when the ignition is ON with the engine OFF in order to perform a bulb check.

Mileage Since DTC Cleared: This parameter displays the mileage that has elapsed since any diagnostic trouble code (DTC) has been cleared from the control modules memory.

Misfire Current Cyl. #1 - #4: The misfire current counters increment at a rate according to the number of possible misfires the powertrain control module (PCM) detects on each cylinder during the last 200 cylinder firing events. The counters may normally display some activity, but the activity should be nearly equal for all the cylinders.

Misfire History Cyl. #1 - #4: The misfire history counters display the total level of misfire that has been detected on each cylinder. The misfire history counters will not update or show any activity until a misfire DTC P0300 has become active. The misfire history counters will update every 200 cylinder firing events.

PCM Reset: The scan tool displays Yes or No. This parameter indicates when the internal PCM resets. The scan tool displays YES when an internal PCM reset occurred. The scan tool displays NO under the normal operating conditions.

Power Enrichment: The scan tool displays Active/Inactive. The scan tool indicates when power enrichment mode is active (moderate to heavy acceleration). Helpful in diagnosing DTC P1171.

Reduced Engine Power: The scan tool displays Active or Inactive. The scan tool displays Active when the PCM receives a signal from the TAC module that a throttle actuator control system fault is occurring. The PCM limits the engine power.

SC Inlet Pressure: The scan tool displays the calculated difference between BARO and SCIP when the ignition is ON, or when the engine is running. At ignition ON, engine OFF, the value will be close to zero since in this state there is no difference between the two. Engine idling, at 1,200 feet of elevation, the BARO is approximately 98 kPa, minus the SCIP at approximately 34 kPa will result in a calculated value of 64 kPa.

SC Inlet Pressure Sensor: The scan tool displays a voltage signal derived from the pressure changes measured in the plenum area after the throttle plate and before the supercharger screws.

Short Term FT: The scan tool displays percentage. The short term fuel trim represents a short term correction to fuel delivery by the powertrain control module (PCM) in response to the amount of time the fuel control oxygen sensor voltage spends above or below the 450 mV threshold. If the oxygen sensor voltage mainly remains less than 450 mV, indicating a lean air/fuel mixture, short term fuel trim increases into the positive range above 0 percent. The PCM adds fuel. If the oxygen sensor voltage stays mainly above the threshold, the short term fuel trim decreases below 0 percent into the negative range. The PCM reduces the fuel delivery in order to compensate for the indicated rich condition. Under certain conditions such as an extended idle and a high ambient temperature, the canister purge may cause the short term fuel trim to read in the negative range during normal operation. The fuel trim values at maximum authority may indicate an excessively rich or lean system.

Short Term FT Avg.: The scan tool displays %. This parameter indicates the average short term fuel trim for this bank. The scan tool will display a value more than 0 if the time is being added to the injector pulse width, increasing the amount of fuel to that bank of the engine to compensate for a lean condition sensed by the oxygen sensors on that bank. The scan tool will display a value less than 0 if time is being subtracted from the injector pulse width, reducing the amount of fuel to the engine to compensate for a rich condition sensed by the oxygen sensors on that bank. A value of 0 percent indicates no compensation is required to operate the engine at the desired air/fuel ratio.

Spark: The scan tool displays the amount of degrees the powertrain control module (PCM) commands the spark advance. The PCM computes the desired spark advance using the following: 1. Engine coolant temperature (ECT) 2. Engine speed (RPM), 3. Load 4. Vehicle speed The PCM adjusts the timing.

Start Up ECT: The scan tool displays the engine coolant temperature (ECT) at the time the engine was started. The powertrain control module (PCM) uses start-up ECT for certain diagnostic trouble codes (DTCs).

Start Up IAT: Indicated the intake air temperature (IAT) at the time that the vehicle was started. Used to determine if the last startup was a cold start. This parameter indicates the ambient air temperature at start-up.

Starter Relay Command: This parameter displays the status of the output driver for the starter relay control circuit. The scan tool will display ON/OFF.

Stoplamp Pedal Switch: This parameter displays the position of the stoplamp pedal switch input to the control module.

Torque Delivered Signal: Represents the PWM signal which indicates the percent of available torque the engine is delivering to the drive wheels. The EBTCM monitors the traction control torque signal to ensure that the PCM is responding properly to the traction control desired torque signal.

Torque Request Signal: Represents the PWM signal from the electronic brake and traction control module (EBTCM). The EBTCM reduces the traction control desired torque signal pulse width when a drive wheel slippage situation is detected. The PCM monitors the traction control desired torque signal and reduces drive wheel slippage as necessary by retarding spark timing, decreasing boost sol. PWM, or increasing air/fuel ratio. The PCM can also turn OFF up to three fuel injectors if the traction control desired torque signal indicates a large enough amount of drive wheel slippage.

Total Misfire Count: This parameter indicates the total level of misfire that has been detected on each cylinder. The misfire history counters will not update or show any activity until a misfire or DTC P0300 has become active. The misfire history counter will update every 200 cylinder firing events.

TP 1 Learned Min: This parameter displays the learned minimum value of TP sensor 1 as recorded by the control module on start-up for the ignition cycle.

TP 2 Learned Min: This parameter displays the learned minimum value of TP sensor 2 as recorded by the control module on start-up for the ignition cycle.

TP Desired Angle: The powertrain control module (PCM) indicates the desired throttle angle commanded by the vehicle operator.

TP Indicated Angle: This parameter displays the angle of the throttle position (TP) in percent. This information is calculated by the control module using the signals from the throttle position sensors. The scan tool will display a low percentage when the throttle plate is closed. The scan tool will display a high percentage when the throttle plate is fully open.

TP Sensor 1: This parameter displays the voltage signal sent to the control module from the sensor used to monitor the position of the throttle plate. This parameter is for sensor 1 of the throttle position (TP) sensor assembly. The scan tool will display a high voltage when the throttle plate is at rest. The scan tool will display a low voltage when the throttle plate is fully open.

TP Sensor  1: This parameter displays the angle of the throttle position (TP) sensor 1 in percent. This information is calculated by the control module using the signal from the throttle position sensor 1. The scan tool will display a low percentage when the throttle plate is closed. The scan tool will display a high percentage when the throttle plate is fully open.

TP Sensors 1 and 2: This parameter displays the results of a control module test that compares the signals from the throttle position (TP) sensors 1 and 2 . The scan tool will display Agree when the signal from TP sensor 1 corresponds with the signal from TP sensor 2. The scan tool will display Disagree when the signal from TP sensor 1 conflicts with the signal from TP sensor 2.

TP Sensor 2: This parameter displays the voltage signal sent to the control module from the sensor used to monitor the position of the throttle plate. This parameter is for sensor 2 of the throttle position (TP) sensor assembly. The scan tool will display a low voltage when the throttle plate is at rest. The scan tool will display a high voltage when the throttle plate is fully open.

TP Sensor 2: This parameter displays the angle of the throttle position (TP) sensor 2 in percent. This information is calculated by the control module using the signal from the throttle position sensor 2. The scan tool will display a low percentage when the throttle plate is closed. The scan tool will display a high percentage when the throttle plate is fully open.

Traction Control Status: This parameter displays the status of the traction control circuit. The scan tool displays active if the PCM receives a signal from the electronic brake and traction control module (EBTCM) requesting torque reduction during a traction control event.

TWC Temperature Calculated: Represents the calculated temperature of the catalytic converter. Useful for determining if the Catalyst Monitor Test has run.

Vehicle Security Status: This parameter displays the status of the vehicle theft deterrent system. The scan tool will display fuel enabled or fuel disabled.

Vehicle Speed Sensor: The scan tool displays km/h and mph. The vehicle speed sensor signal is converted into km/h and mph for display on the scan tool.

Warm-ups w/o Emission Faults: This parameter counts the number of warm-up cycles without an emission fault present. The counter increments to 255 and rolls back to 0 unless a fault occurs. If a fault occurs, the counter reverts back to 0 until the fault is corrected. Clearing the information with a scan tool or a loss of power to the PCM also resets the counter to 0. The scan tool displays counts. This display indicates the number of warm-up cycles without a emission failure.

Warm-ups w/o Non-Emission Faults: This parameter counts the number of warm-up cycles without a non-emission fault present. The counter increments to 255 and rolls back to 0 unless a fault occurs. If a fault occurs, the counter reverts back to 0 until the fault is corrected. Clearing the information with a scan tool or a loss of power to the PCM also resets the counter to 0.