The Engine Scan Tool Data Definitions contain 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 appear more than once, or in more than one data list, in order to group certain related parameters together.

3X Crank Sensor: The scan tool displays 1200-10,000 RPM. This signal is calculated from the 7X pulses and is fed to the PCM by the ignition control module (ICM). This is used by the powertrain control module (PCM) to calculate RPM at engine speeds of more than 1200 RPM and to initiate injector pulses.

24X Crank Sensor: The scan tool displays 0-1600 RPM. Displays the engine speed calculated from the 24X Reference signal PCM input. Should nearly match engine speed up to approximately the 1600 RPM limit.

A/C High Side Pressure Sensor: The scan tool displays 0.00-5.00 volts. This represents the air conditioning (A/C) refrigerant pressure sensor signal. The amount of pressure indicates the load that the A/C compressor is placing on the engine. The PCM uses this information to adjust the idle and to control the cooling fans.

A/C Pressure Disable: The scan tool displays YES or NO, indicating that the PCM has disabled the A/C Compressor Clutch.

A/C Relay Circuit Status: The scan tool displays OK, Fault, or Invalid State. These parameters describe the condition of the control circuit.

A/C Relay Command: The scan tool displays YES or NO, indicating the state of the A/C request input circuit from the HVAC controls. The PCM uses the A/C request signal to determine if the A/C compressor operation is being requested.

A/C Request Signal: The scan tool displays YES or NO, indicating an A/C request

Air/Fuel Ratio: The scan tool displays 0.0-25.5. The Air/Fuel Ratio indicates the PCM commanded value. In Closed Loop mode, the air fuel ratio should be around 14.2-14.7. A lower air fuel ratio indicates a richer commanded mixture, which may be seen during power enrichment or 3-way converter (TWC) protection modes. A higher ratio indicates a leaner commanded mixture. This can be seen during Decel Fuel mode.

BARO: The scan tool displays 10-105 kPa (0.00-5.00  volts). The barometric pressure (BARO) reading is determined from the manifold absolute (MAP) pressure sensor signal monitored during key up and wide open throttle (WOT) conditions. The barometric pressure is used to adjust the fuel delivery and the spark advance to compensate for altitude changes.

Cam Sensor Signal Present: The scan tool displays YES or NO. If the PCM does not receive a cam signal from the ignition control module (ICM), the scan tool displays NO.

Commanded Gen: The scan tool displays ON or OFF. OFF indicates that the PCM has commanded the generator control circuit OFF.

Current Gear: The scan tool displays 0-4. The scan tool displays the selected transmission gear.

Cycles of Misfire Data: The scan tool displays counts from 0-99. The number represents the number of misfires.

Cylinder 1-6 Injector Circuit History: The scan tool displays OK, Stuck Low (open), or Stuck High. These parameters describe the condition of each injector control circuit. If a fault is detected, the scan tool will list which the fault type with the corresponding cylinder.

Cylinder 1-6 Injector Circuit Status: The scan tool displays OK, Stuck Low (open), or Stuck High. These parameters describe the condition of each injector control circuit.

Decel Fuel Cutoff: The scan tool displays ACTIVE or INACTIVE. ACTIVE indicates the PCM has detected conditions appropriate to operate in Deceleration Fuel mode. The PCM will command Deceleration Fuel mode when a sudden decrease in throttle position has been detected while the vehicle is traveling at more than 40 km/h (25 mph). While in Deceleration Fuel mode, the PCM decreases the amount of fuel delivered by entering Open Loop and decreasing the injector pulse width.

Desired EGR Position: The scan tool displays 0-100 percent, representing the EGR pintle position that the PCM is commanding. The Desired EGR Position should remain close to the Actual EGR Position.

Desired Idle Speed: The scan tool displays 0-3187 RPM, representing the idle speed that is commanded by the PCM. The PCM will compensate for various engine loads based upon the engine coolant temperature to keep the engine at the desired idle speed.

Driver Module 1/2/3/4 Status: The scan tool displays Enabled, Off-High Volts, Off High Temp, or Invalid State. This parameter describes the internal PCM driver module condition. This module controls all the relays and solenoids listed below the driver module parameter in the scan tool Output Driver Data List up to the next driver module.

ECT Sensor: The scan tool displays -40° to +151° C (-40° to +304° F). The engine coolant temperature (ECT) sensor is mounted in the coolant stream. The PCM applies 5 volts to the ECT sensor circuit. The sensor is a thermistor which changes internal resistance as the temperature changes. When the sensor is cold, the PCM monitors a high signal voltage and interprets the signal as a cold engine. As the sensor warms, the voltage signal decreases and the PCM interprets the lower voltage as a warm engine.

EGR Learned Minimum Position: The scan tool displays 0.0-5.0 volts, representing the learned voltage that the PCM uses to determine whether or not the EGR valve is fully closed. If the desired EGR position is 0 percent and a difference of more than 0.4 volts between EGR feedback and EGR closed valve pintle position is detected, DTC P1406 will set.

EGR Flow Test Count: The scan tool displays 0-255 counts, indicating the number of EGR flow test samples collected during the current ignition cycle. The maximum number of samples allowed is 1 during normal operation. If the PCM battery feed has been disconnected or a DTC P0401 has been cleared, several EGR flow test samples will be allowed during the next ignition cycle. This allows repair verification during a single ignition cycle.

EGR Position Sensor: The scan tool displays 0-100 percent, representing the actual position of the exhaust gas recirculation (EGR) pintle in percent. 0 percent displayed indicates a fully extended pintle and the EGR valve closed.

EGR Position Sensor: The scan tool displays 0.00-5.00 volts, indicating the signal voltage of the EGR pintle position sensor being monitored by the PCM. A low voltage indicates a fully extended pintle. A voltage near 5 volts indicates a fully retracted pintle.

EGR Position Variance: The scan tool displays 0-100 percent, indicating the difference between the desired EGR position and actual EGR position currently being monitored by the PCM. If the EGR position error reaches an unacceptable level, DTC P1406 will set.

EGR Solenoid Command: The scan tool displays 0-100 percent, representing the EGR valve driver pulse width modulated (PWM) signal from the PCM. A duty cycle of 0 percent indicates that no EGR flow is being commanded, a 100 percent duty cycle indicates the maximum EGR flow is commanded.

Engine Load: The scan tool displays 0-100 percent. The engine load is calculated by the PCM from the engine speed and the MAF sensor readings. The engine load should increase with an increase in RPM or in air flow.

Engine Oil Level Switch: The scan tool displays OK or Low IN IPC, indicating the oil level as determined by the engine oil level sensor.

Engine Oil Life Remaining: The scan tool displays percents, indicating the remaining oil life until the next recommended oil change.

Engine Oil Pressure Switch: The scan tool displays OK/Low/High, indicating the oil pressure as determined by the oil sending unit.

Engine Run Time: The scan tool displays 00:00:00-99:99:99 Hrs:Min:Sec. indicating the time elapsed since the engine was started. If the engine is stopped, the Engine Run Time will be reset to 00:00:00.

Engine Speed: The scan tool displays 0-9999 RPM. The engine speed is computed by the PCM from the 3X reference input. The engine speed should remain close to the desired idle under various engine loads with the engine idling.

EVAP Purge Solenoid Circuit Status: The scan tool displays OK, Fault, or Invalid State. These parameters describe the condition of the control circuit.

EVAP Purge Solenoid Command: The scan tool displays 0-100 percent, representing the PCM commanded PWM duty cycle of the EVAP purge valve. 0 percent displayed indicates no purge. 100 percent displayed indicates full purge.

FC Relay 1 Command: The scan tool displays ON or OFF, representing the PCM commanded state of both fans.

FC Relay 2 and 3 Command: The scan tool displays ON or OFF, represents the PCM commanded state of both fans.

FC Relay 1 Command: The scan tool displays OK, Fault, or Invalid State. These parameters describe the condition of the control circuit.

FC Relay 2 and 3 Command: The scan tool displays OK, Fault, or Invalid State. These parameters describe the condition of the control circuit.

Fuel Pump Relay Circuit History Status: The scan tool displays OK, Stuck Low (open), or Stuck High. These parameters describe the condition of the fuel pump control circuit.

Fuel Pump Relay Circuit Status: The scan tool displays OK, Stuck Low (open), or Stuck High. These parameters describe the condition of the fuel pump control circuit. If a fault is detected the scan tool will list which is the fault type.

Fuel Pump Relay Command: The scan tool displays ON or OFF, indicating the PCM commanded state of the fuel pump relay control circuit.

Fuel Trim Cell: The scan tool displays 1,2,3,4, these cells change during different conditions, accelerate, decelerate, idle.

Fuel Trim Learn: The scan tool displays Enabled or Disabled. When conditions are appropriate for enabling long term (LT) fuel trim corrections, the Fuel Trim Learn will display as Enable. This indicates that the long term fuel trim is responding to short term (ST) fuel trim. If the Fuel Trim Learn displays Disable, the long term fuel trim will not respond to changes in short term fuel trim.

Generator L Terminal Signal Command: The scan tool displays ON or OFF, represents the PCM commanded state of the L Terminal.

HO2S 1:  The scan tool displays 0-1132 mV, representing the output voltage of the fuel control oxygen sensor . The reading should fluctuate constantly within a range of 10 mV and 1000 mV while operating in Closed Loop.

IAC Position: The scan tool displays 0-255 counts, indicating the commanded position of the idle air control (IAC) pintle in counts. A larger number of counts means that more air is being commanded through the idle air passage. The IAC position should respond fairly quickly to changes in engine load in order to maintain desired idle RPM.

IAT sensor: The scan tool displays -40° to +151° C (-40° to +304° F). The PCM converts the resistance of the intake air temperature (IAT) sensor to degrees. The PCM uses the IAT sensor to adjust the fuel delivery and the spark timing according to the incoming air density. The IAT is also compared to the ECT at startup to identify cold starts for the HO2S heater and the EVAP diagnostics.

Ignition 1 Signal: The scan tool displays 0-25.5 volts, representing the system voltage measured by the PCM at the PCM ignition feed.

Ignition Mode: The scan tool displays BYPASS or IC, indicating the commanded state of the Bypass signal output from the PCM. When BYPASS is displayed, the ignition control module (ICM) is controlling the spark advance at a fixed 10 degrees before top dead center (BTDC) Bypass mode. IC displayed indicates that the PCM has requested control of the spark advance (IC mode). The ignition control module (ICM) determines the correct operating mode based upon the level of voltage that the PCM applies to the ICM bypass circuit. The PCM provides 5 volts to the ICM bypass circuit when conditions are appropriate for PCM control of spark timing (IC mode). If the PCM does not apply 5 volts to the bypass circuit, or if the ignition control module does not receive the 5 volts, the module will control the spark timing.

Injector PWM: The scan tool displays 0-1000 msec, indicating the amount of time the PCM is commanding each injector ON during each engine cycle. A longer injector pulse width will cause more fuel to be delivered. The injector pulse width should increase with an increased engine load.

Knock Retard: The scan tool displays 0.0-25.5 degrees, indicating the amount of spark the PCM is removing from the IC spark advance in response to the signal from the knock sensors (KS). The traction control system desired torque signal from the electronic brake and traction control module (EBTCM) may cause Knock Retard to display as a value more than 0.0 degrees if the traction control is active.

Long Term FT: The scan tool displays -10 to +10 percent. The long term (LT) fuel trim is derived from the short term (ST) fuel trim value and represents a long-term correction of the fuel delivery. A value of 0 percent indicates that fuel delivery requires no compensation to maintain the PCM commanded air/fuel ratio. A negative value significantly less than 0 percent indicates that the fuel system is rich and fuel delivery is being reduced. A positive value significantly more than 0 percent indicates that a lean condition exists and the PCM is compensating by adding fuel. Because the long term fuel trim tends to follow the short term fuel trim, a value in the negative range due to canister purge at idle should not be considered unusual. The maximum authority of the PCM to control the long term fuel trim allows a range between -10 and +10 percent. Fuel trim values at or near the maximum authority may indicate an excessively rich or lean system.

Loop Status:  The scan tool displays OPEN or CLOSED. Closed Loop indicates that the PCM is controlling the fuel delivery according to the oxygen sensor voltage. In Open Loop, the PCM ignores the oxygen sensor voltage and bases the amount of fuel delivered on the inputs of the TP sensor, the engine coolant, and the MAF sensor.

MAF Sensor: The scan tool displays 0.0-512 g/s. 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 scan tool displays 0-32000 Hz. The MAF sensor input signal to the PCM is a frequency which varies from around 3000 Hz at idle to more than 7000 Hz at wide open throttle (WOT). The PCM converts the frequency signal to grams per second to be displayed on the scan tool as MAF.

MAP Sensor: The scan tool displays 10-105 kPa (0.00-4.97 volts). The manifold absolute pressure (MAP) sensor measures the change in the intake manifold pressure from the engine load, the EGR flow, and any speed changes. As the intake manifold pressure increases, the intake vacuum decreases, resulting in a higher MAP reading. The MAP sensor signal is used to monitor the intake manifold pressure changes during the EGR flow test, to update the barometric pressure (BARO) reading, and as an enabling factor for many of the diagnostics.

MIL Circuit status: The scan tool displays OK, Fault, or Invalid State in ODD. These parameters describe the condition of the control circuit.

MIL Command:  The scan tool displays ON or OFF in Eng 2, indicating the PCM commanded state of the malfunction indicator lamp (MIL).

Misfire Current Cyl 1-6: The scan tool displays 0-198 counts. The misfire current counters indicate the number of cylinder firing events detected as possible misfires on each cylinder during the last 200 crankshaft revolutions. The number that the counters display are twice the actual number of misfire events detected. The counters may normally display some activity, but the activity should be very low and nearly equal for all the cylinders.

Misfire History Cyl 1-6: The scan tool displays 0-65535 counts. The misfire history counters indicate the total level of misfire that has been detected on each cylinder. The number that the counters display are twice the actual number of misfire events detected. The misfire history counters will not update or show any activity until a misfire DTC P0300 has become active. The misfire history counters will be updated every time a 200 crankshaft revolution misfire test failure is detected.

Number Of DTC's: The scan tool displays the Diagnostic Trouble Codes (DTC) that are set.

PCM Reset: The scan tool displays Pass or Fail, indicating the condition of the PCM random access memory.

Power Enrichment: The scan tool displays ACTIVE or INACTIVE. ACTIVE displayed indicates that the PCM has detected conditions appropriate to operate in the Power Enrichment mode. The PCM will command the Power Enrichment mode when a large increase in throttle position and load is detected. While in Power Enrichment mode, the PCM will increase the amount of fuel delivered by entering Open Loop and increasing the injector pulse width. This is done to prevent a sag or hesitation from occurring during acceleration.

Short Term FT: The scan tool displays -10 to +10 percent. The short term fuel trim represents a short term correction to the fuel delivery by the PCM in response to the amount of time the fuel control oxygen sensor voltage spends at more than or less than the 450 mV threshold. If the oxygen sensor voltage has mainly remained less than 450 mV, indicating a lean air/fuel mixture, the short term fuel trim will increase to more than 0 percent and the PCM will add fuel. If the oxygen sensor voltage stays mainly above the threshold, the short term fuel trim will decrease to less than 0 percent while the PCM reduces fuel delivery in order to compensate for the indicated rich condition. Under certain conditions, such as extended idle and high ambient temperatures, the canister purge may cause the short term fuel trim to read in the negative range during normal operation. The maximum authority of the PCM to control fuel trim allows a range between -10 percent and +10 percent. Fuel trim values at the maximum authority may indicate an excessively rich or excessively lean system.

Spark: The scan tool displays -64 to +64 degrees, indicating the spark timing being commanded by the PCM on the IC circuit. A negative value indicates degrees Before Top Dead Center (BTDC) or spark advance. A positive value indicates degrees After Top Dead Center (ATDC) or spark retard. Because the ignition control module (ICM) sets the spark advance at a fixed value of 10 degrees BTDC while operating in Bypass mode, the displayed spark advance only reflects the true spark timing when the PCM has commanded IC mode.

Start-Up ECT: The scan tool displays -40° to +151° C (-40° to +304° F), indicating the engine coolant temperature (ECT) at the time that the vehicle was started. The start-up ECT is used by the HO2S diagnostic to determine if the last startup was a cold start.

Start-Up IAT: The scan tool displays -40° to +151° C (-40° to +304° F), indicating the intake air temperature (IAT) at the time that the vehicle was started. The start-up IAT is used by the HO2S diagnostic to determine if the last startup was a cold start.

Starter Enable Relay Circuit Status: The scan tool displays OK , Fault or Invalid State.These parameters describe the condition of the Relay Circuit.

Starter Relay Command: the scan tool displays ON or OFF, indicating the PCM commanded state of the Starter Relay.

TCC Brake Pedal Switch: The scan tool displays APPLIED or RELEASED, indicating the brake pedal position. When the brake pedal is depressed a signal voltage is sent to the PCM.

TCC PWM Solenoid Command: The scan tool displays ON or OFF, indicating the commanded state of the transaxle torque convertor clutch (TCC).

TP Sensor : The scan tool displays 0.5-5.00 volts, corresponding to the voltage being monitored by the PCM on the TP sensor signal circuit. The scan tool displays 0-100 percent. The TP Angle is computed by the PCM from the TP sensor voltage. The TP angle should be 0 percent at idle and 100 percent at wide open throttle (WOT).

Vehicle Speed Sensor: The scan tool displays 0-255 km/h (0-155 mph). The vehicle speed sensor signal is converted into mph and km/h for display.

VTD Fuel Disable: The scan tool displays ACTIVE or INACTIVE. The theft deterrent fuel enable circuit is an input from the vehicle theft deterrent control module that signals the PCM to enable the injectors if the proper signal is received. The scan tool will normally display INACTIVE. If the vehicle theft deterrent control module does not sent the correct theft deterrent fuel enable signal to the PCM, the display will switch to ACTIVE and the fuel system may be disabled. Refer to DTCs  P1626, P1630 and P163` or Refer to Vehicle Theft Deterrent diagnosis for further information.