For 1990-2009 cars

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/C Refrigerant Pressure--Range 0-5 Volts: The A/C High Side displays the pressure value of the A/C refrigerant pressure sensor. The A/C refrigerant pressure helps diagnose DTC P0530.
A/C Relay Command--Range On/Off: The A/C Relay represents the commanded state of the A/C clutch control relay. The A/C clutch should be engaged when the scan tool displays ON.
A/C Request Signal--Range Yes/No: A/C Request--This displays if engine control module (ECM) has received an A/C request from body control module (BCM) YES or NO.
Air Flow Calculated--Range 0-512 grams/second: The calculated airflow is a calculation based on manifold absolute pressure (MAP). The calculation is used in several diagnostics to determine when a sufficient engine load has been achieved to run the diagnostic.
Air Fuel Ratio--Range 0:1-25.5:1: The air fuel ratio indicates the air to fuel ratio based on the oxygen sensor (O2S 1) inputs. The engine control module (ECM) uses the fuel trim to adjust fueling in order to maintain near an air fuel ratio of 14.7:1.
BARO--Range 11-105 kPa, 0-5.0 Volts: The barometric pressure (BARO) sensor measures the change in the intake manifold pressure which results from altitude changes. This value is updated at ignition ON and also at wide open throttle (WOT).
CMP Resync Counter--Range 0-255 Counts: The camshaft position (CMP) resync counter displays the number of times the engine control module (ECM) had to resync with the CMP sensor. The CMP Resync Counter is helpful in diagnosing DTC P0341.
Calculated Converter Temperature: Represents the calculated temperature of the catalytic converter. Useful for determining if the Catalyst Monitor Test has run.
Cooling Relay Command Relay--Range On/Off: The fan control (FC) relay is commanded by the engine control module (ECM). FC relay 1 displays the command as ON or OFF.
Cooling Fan Relay CMD: Displays ON if the ECM is commanding the cooling fan relay On.
Crank Learned: Displays YES if the ECM has learned the variation between crankshaft reluctor notch spacing. Learning the crankshaft is vital to correct misfire diagnostics.
Cruise Clutch Command: Displays YES if the ECM is commanding the cruise control module clutch On.
Cruise Delta: Displays the difference between the cruise set speed and the actual vehicle speed.
Cruise Direction Command: Displays YES if the ECM is commanding cruise direction.
Cruise In Released State: Displays YES if the ECM has disengaged cruise.
Cruise Resume/Accel: Displays ON if the RES/ACCEL switch is depressed.
Cruise Set Speed: Indicates the set vehicle cruise speed.
Cruise Set/Coast: Displays ON if the SET/COAST switch is depressed.
Cruise Switch: Displays ON if the CRUISE ON/OFF switch is On.
Cruise Switch--ON/OFF: The Stepper Cruise display indicates if the engine control module (ECM) is allowing the cruise operation. The ECM has the ability to disable the cruise control under certain conditions.
Cruise Switch Voltage: Indicates the value of the cruise control signal voltage at the ECM.
Desired Idle Speed-- 0-3,187 RPM: The engine control module (ECM) commands the idle speed. The ECM compensates for various engine loads in order to maintain the desired idle speed. The actual engine RPM speed should remain close to the desired idle under the various engine loads with the engine idling.
Dist. Since Code Clear: Indicates the number of miles the vehicle has traveled since the last time the ECM DTCs were cleared.
ECT--Range -40 to +151°C (-40 to +304°F): The engine coolant temperature (ECT) sensor sends engine temperature information to the engine control module (ECM). The ECM supplies 5 volts to the ECT sensor circuit. The sensor is a thermistor which changes internal resistance as temperature changes. When the sensor is cold, internal resistance high, the ECM monitors a high voltage which is interpreted as a cold engine. As the sensor warms, internal resistance decreases, the voltage signal will decrease and the ECM will interpret the lower voltage as a warm engine.
Engine LOAD--Range 0-100 Percent: Indicates engine load based on MAP. The higher the percentage, the more load the engine is under.
Engine Oil Life Remaining--Range 0-100 Percent: This display represents the engine oil life index that is calculated and maintained by the engine control module (ECM).
Engine Oil Life Reset: Displays YES when the oil life reset switch in the UHFB is being depressed (switch closed).
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 been running. When the engine stops running the timer resets to zero.
Engine Speed--Range 0-16,384 RPM: Engine Speed is computed by the engine control module (ECM) from the fuel control reference input. The engine speed should remain close to desired idle under the various engine loads with the engine idling.
EVAP Large Leak: Indicates the PASS or FAIL result of the EVAP large leak diagnostic during the EVAP diagnostic system test. NOT RAN means the test has not run this ignition and INV means the test results were invalid. A FAIL indicates a large leak is present.
EVAP Purge Solenoid: Displays ON if the ECM is commanding a duty cycle to the EVAP purge solenoid.
EVAP Purge Solenoid DC: Indicates the EVAP purge solenoid On-time percentage the ECM is commanding.
EVAP Purge Solenoid Command--Range 0-100 Percent: Indicates the engine control module (ECM) command of the evaporative emission (EVAP) purge valve solenoid in order to control the EVAP canister purge function. At 0 percent the valve is commanded fully closed. 100 percent implies that the valve is fully open.
EVAP Purge Valve Leak: Indicates the PASS or FAIL result of the EVAP purge solenoid diagnostic test during the EVAP diagnostic system test. NOT RAN means the test has not run this ignition and INV means the test results were invalid. A FAIL most likely indicates the EVAP purge solenoid is stuck open.
EVAP Small Leak: Indicates the PASS or FAIL result of the EVAP small leak diagnostic during the EVAP diagnostic system test. NOT RAN means the test has not run this ignition and INV means the test results were invalid. A FAIL indicates a small leak is present.
EVAP Tank Vac. Slope: Indicates the rate at which the vacuum in the fuel tank during the EVAP system small and large leak diagnostic test is decreasing (losing vacuum). Units are in millimeters of mercury per second.
EVAP Vent Blockage: Indicates the PASS or FAIL result of the EVAP vent solenoid diagnostic test during the EVAP diagnostic system test. NOT RAN means the test has not run this ignition and INV means the test results were invalid. A FAIL most likely indicates the EVAP vent solenoid is stuck closed or an EVAP line from the vent to the fuel tank is kinked.
EVAP Vent Solenoid: Displays ON if the ECM is commanding the EVAP vent solenoid On.
EVAP Vent Solenoid Command--Range Venting/Non-venting: Indicates the engine control module (ECM) command of the evaporative emission (EVAP) vent solenoid allowing fresh outside air to the EVAP canister during the purge mode. The EVAP vent solenoid allows the diagnostic to pull a vacuum on the fuel tank by closing the vent solenoid.
Fuel Level Sensor-- Range 0-100 Percent: The fuel level sensor monitors the fuel level in the tank. Several of the enhanced EVAP system diagnostics are dependent upon the correct fuel level.
Fuel Level Sensor: Indicates the value of the fuel level sensor voltage at the ECM based on fuel tank level.
Fuel Pump Relay Command-- Range ON/OFF: Indicates the engine control module (ECM) command of the fuel pump relay.
Fuel Tank Pressure Sensor-- Range -25.89 to +32.45 mm Hg: The fuel tank pressure (FTP) sensor measures the difference between the pressure or vacuum in the fuel tank and the outside air pressure.
Fuel Tank Pressure Sensor--Range - 0.0 to +5.0 Volts: The fuel tank pressure (FTP) sensor measures the difference between the pressure or the vacuum in the fuel tank and the outside air pressure. When the air pressure in the fuel tank equals the outside air pressure, the output voltage of the sensor is 1.3-1.7 volts.
Fuel Trim Cell--Range 0-22: A fuel trim cell depends upon the engine speed and the manifold absolute pressure (MAP) sensor readings. RPM vs. MAP is broken down into 22 fuel trim cells. The fuel trim cell indicates which cell is currently active.
Generator L Terminal Signal--Range Inactive/Active: The generator L terminal indicates whether the engine control module (ECM) is allowing the generator to operate. The ECM can disable the generator under certain conditions to ease starting. Inactive indicates that the ECM is allowing generator operation, while active indicates that the ECM is not allowing generator operation.
Generator F Terminal Signal--Range 0-100 Percent: Indicates the amount of ON time the engine control module (ECM) is commanding the generator. The higher the percentage the longer the generator is being commanded ON.
High Spark Modifier: LOW, MID and HIGH SPARK MODIFIERS are adaptive spark retard values used to control engine spark knock. The HIGH SPARK MODIFIER should display 0 degrees if no spark retard is needed. The high spark modifier is used for high engine speeds. The adaptives are based on ECT and will reset to 0 degrees during cold temperatures. If a hot restart occurs, a percentage of the learned adaptive will be used. The ECM will always work back to zero compensation or no spark retard.
HO2S 1--Range 0-1132 mV: The front heated oxygen sensor (HO2S) 1 reading represents the exhaust oxygen sensor output voltage. This voltage will fluctuate constantly between 100 mV, lean exhaust to 900 mV, rich exhaust, when operating in a Closed Loop.
HO2S 2-- Range 0-1132 mV: The rear heated oxygen sensor (HO2S) 2 represents the exhaust oxygen output voltage past the catalytic converter. This voltage remains inactive, or the voltage will appear lazy within a range of 100 mV, lean exhaust and 900 mV, rich exhaust, when the system is operating in a Closed Loop.
HO2S 1 Heater Command--Range On/Off: Indicates the engine control module (ECM) command of the heated oxygen sensor (HO2S) 1 heater.
HO2S 2 Heater Command-- Range On/Off: Indicates the engine control module (ECM) command of the heated oxygen sensor (HO2S) 2 heater.
HO2S 1 Heater Current--Amps: The parameter displays the current through the control module when the HO2S sensor 1 heater is commanded ON by the control module. HO2S 1 Heater 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 Current--Amps: The parameter displays the current through the control module when the HO2S sensor 2 heater is commanded ON by the control module. HO2S 2 Heater 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.
IAC Position--Range 0-255 Counts: The idle air control (IAC) pintle position command from the engine control module (ECM) is displayed in counts. The higher the counts read, the more the commanded idle speed is. The IAC responds fairly quickly to changes in the engine load in order to maintain the desired idle RPM.
IAC Position W/O A/C: Indicates the learned idle air control position with the A/C Off.
IAC Position With A/C: Indicates the learned idle air control position with the A/C On.
IAT Sensor--Range -40 to +151°C (-40 to +304°F): The engine control module (ECM) converts the resistance of the intake air temperature (IAT) sensor to degrees in the same manner as the engine coolant temperature (ECT) sensor. Intake air temperature is used by the ECM to adjust fuel delivery and spark timing according to incoming air density.
Ignition 1 Signal--Range 0-25.5 Volts: The ignition volts represents the system voltage measured by the engine control module (ECM) at the ignition feed circuit.
Injector PWM -- Range 0-999.9 mS: 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.
Injector 1-4 Command--On/Off: Indicates the engine control module (ECM) command on the fuel injectors.
KS Noise: Indicates the level of normal noise as seen by the knock sensor at idle. The higher the count value, the higher the amplitude of the noise. Normal noise levels will vary with the SOHC and DOHC engines.
Knock Retard--Range 0-90 Degrees: The Adaptive Knock Retard indicates the long term amount of the spark advance the engine control module (ECM) removes from the ignition control (IC). The ECM responds to the knock sensor (KS) signal.
Lean/Rich Avg. Time: Indicates the average time for the O2S-1 to transition from under 300 mV to over 600 mV during the last test sample.
Lean/Rich Transitions: Indicates the number of times the O2S-1 transitioned from under 300 mV to over 600 mV during the last test sample.
Long Term FT--Range 0-255 (-100 to +100 Percent): The long term FT is derived from the short term FT value. The long term FT is used for the long term correction of the fuel delivery. A value of the 128 counts, 0 percent, indicates that the fuel delivery requires no compensation in order 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. The engine control module (ECM) is decreasing the injector pulse width. A value above 128 counts indicates that a lean condition exists for which the ECM is compensating.
Loop Status--Range Open/Closed: A Closed Loop displayed indicates that the engine control module (ECM) is controlling the fuel delivery according to the oxygen sensor (O2S) 1 voltage. The ECM controls the fuel delivery air to fuel ratio as close to 14.7:1 as possible.
Low Coolant Level: Displays YES if the coolant in the coolant surge tank is low (switch open).
Low Spark Modifier: LOW, MID and HIGH SPARK MODIFIERS are adaptive spark retard values used to control engine spark knock. The LOW SPARK MODIFIER should display 0 degrees if no spark retard is needed. The low spark modifier is used for low engine speeds. The adaptives are based on ECT and will reset to 0 degrees during cold temperatures. If a hot restart occurs, a percentage of the learned adaptive will be used. The ECM always works back to zero compensation or no spark retard.
M/T Clutch Disengaged: Displays YES if the ECM has detected engine flare as a result of the clutch pedal being depressed. There is NO clutch pedal input to the ECM.
MAP Sensor--Range 11-105 kPa, 0-5.0 Volts: The manifold absolute pressure (MAP) sensor measures the change in the intake manifold pressure which results from engine load and speed changes. As the intake manifold pressure increases, the air density in the intake also increases and additional fuel is required.
MIL Command--Range ON/OFF: Indicates whether the engine control module (ECM) is commanding the malfunction indicator lamp (MIL) ON or OFF.
Mid Spark Modifier: LOW, MID and HIGH SPARK modifiers are adaptive spark retard values used to control engine spark knock. The MID SPARK MODIFIER should display 0 degrees if no spark retard is needed. The mid spark modifier is used for mid engine speeds. The adaptives are based on ECT and will reset to 0 degrees during cold temperatures. If a hot restart occurs, a percentage of the learned adaptive will be used. The ECM always works back to zero compensation or no spark retard.
Mileage Since DTC Cleared: The scan tool displays km or miles. This parameter indicates the mileage accumulated since an emission DTC cleared. The powertrain control module (PCM) stores this mileage in the Freeze Frame and Failure Records memory.
Mileage Since First Fail: The scan tool displays km or miles. This parameter indicates the mileage accumulated since an emission DTC first failed. The powertrain control module (PCM) stores this mileage in the Freeze Frame and Failure Records memory.
Mileage Since Last Fail: The scan tool displays km or miles. This parameter indicates the mileage accumulated since an emission DTC last failed. The powertrain control module (PCM) stores this mileage in the Failure Records memory.
Mileage Since MIL Request: The scan tool displays km or miles. This parameter displays the mileage accumulated since the powertrain control module (PCM) requested the malfunction indicator lamp (MIL) to illuminate. The PCM stores the mileage in the Failure Records memory.
Misfire Current #1-4--Range 0-255 Counts: Indicates the number of current misfires that are present in the indicated cylinder. Increments only when misfire is current.
Misfire Enabled: Displays YES when the ECM has detected that all of the misfire enable criteria have been met. Parameters can be found under P0300 DTC PARAMETERS.
Misfire History #1-4--Range 0-255 Counts: Indicates the number of misfires that have occurred after 195 current misfires have been counted. The current misfire counter will add the misfires to the history misfire counter after 195 total misfires have taken place. If 1 cylinder is misfiring, the misfiring current counter will have 195 misfires counted before adding to its history counter. If 2 cylinders are misfiring, the misfiring current counters will add to their history counters after 97 misfires. Increments only after a misfire diagnostic trouble code (DTC) has been set.
Park/Neutral Switch: Displays P-N or R-D-L as indicated from the transaxle range switch.
Rich/Lean Avg. Time: Indicates the average time for the O2S-1 to transition from over 600 mV to under 300 mV during the last test sample.
Rich/Lean Transitions: Indicates the number of times for the O2S-1 to transition from over 600 mV to under 300 mV during the last test sample.
Short Term FT--Range 0-255 (-100 to +100 Percent): Short term FT represents a short term correction to fuel delivery by the engine control module (ECM) in response to the amount of time the oxygen sensor (O2S) voltage spends above or below the 450 mV threshold. If the oxygen sensor has mainly been below 450 mV, indicating a lean air/fuel mixture, short term FT will increase to tell the ECM to add fuel. If the oxygen sensor voltage stays mainly above the threshold, the ECM will reduce fuel delivery to compensate for the indicated rich condition.
Spark--Range 64 to -64 Degrees: This is a display of the spark advance ignition control (IC) calculation which the engine control module (ECM) is programming in the ignition system. The desired spark advance is computed using data such as engine temperature, RPM, engine load, vehicle speed and operating mode.
Start Up ECT: Indicates the engine coolant temperature (ECT) at engine start up.
Steering Assist Sol. DC: Indicates the steering assist solenoid On-time percentage the ECM is commanding. Under 16 km/h (10 mph), the duty cycle will be 0% or full assist. Over 113 km/h (70 mph) the duty cycle will be 100% or no assist. In between speeds will vary.
TP Sensor--Range 0-100 Percent: The engine control module (ECM) computes the throttle position (TP) from the TP sensor voltage input. The TP angle will auto zero to 0 percent at idle when the TP voltage is below 0.90 volt. The TP angle will read 100 percent at wide open throttle (WOT).
TP Sensor--Range 0.0-0.5 Volts: The engine control module (ECM) uses the TP sensor to determine the amount of the throttle demanded by the operator of the vehicle. The throttle position (TP) sensor reads between 0.36-0.96 volt at idle to above 4 volts at wide open throttle (WOT).
TR Switch--Range High or Low: A transaxle mounted switch is used as an input to let the engine control module (ECM) know what position the gear select lever is in. The scan tool status will switch from High to Low as different combinations are met. In Park, PRNDL P and A will be Low and B and C will be High.
Vehicle Speed Sensor--Range 0-255 km/h, 0-255 mph: The vehicle speed sensor (VSS) signal is converted into km/h (mph) for display. The vehicle speed output from the engine control module (ECM) is 4,000 pulses per mile. The scan tool uses the Class 2 serial data from the ECM to obtain vehicle speed, while the instrument panel cluster, cruise control module and multi-function alarm module use the 4,000 ppm output.
VTD Fuel Cutoff--Range No/Yes: Indicates if the vehicle theft deterrent (VTD) module has received proper information to enable or disable fuel.