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.

4WD: The scan tool displays Enabled or Disabled. The transfer case should be in 4WD when the scan tool displays Enabled.

4WD Low: The scan tool displays Enabled or Disabled. The transfer case should be in 4WD Low when the scan tool displays Enabled.

A/C Compressor Cycling Switch: The scan tool displays Open or Closed. This parameter displays the state of the A/C Compressor Cycling Switch. The A/C Compressor Cycling Switch is a normally closed switch.

A/C Relay Command: The scan tool displays On or Off. This parameter displays the PCM commanded state of the A/C clutch control relay. When the scan tool displays ON, the A/C clutch should be engaged.

A/C Sec. High Press. Switch: The scan tool displays Open or Closed. This parameter displays the state of the A/C Secondary High Pressure Switch. The A/C Secondary High Pressure Switch is normally open.

A/C Request: The scan tool displays Yes or No. The A/C Request displays the state of the A/C request input circuit from the HVAC controls. The PCM uses the A/C request signal in order to determine whether the A/C compressor operation is being requested.

Actual EGR Position: The scan tool displays a range of 0%-100%. The PCM supplies a Pulse Width Modulated (PWM) duty cycle to control the EGR valve. 0% indicates no EGR flow; 100% indicates full EGR flow.

Air Fuel Ratio: The scan tool displays the ratio of the air to fuel. A typical ratio is about 14.7:1.

AIR Pump Relay: The scan tool displays On or Off. The scan tool displays ON when the PCM grounds the AIR pump relay control circuit. The scan tool displays OFF when the PCM disables the ground circuit.

BARO: The scan tool displays a range of 10-105 kPa and 0.00-5.00 volts. The Barometric Pressure reading is determined from the MAP sensor signal. The PCM monitors the MAP signal during key up or Wide-Open Throttle (WOT) conditions. The Barometric Pressure compensates for altitude differences.

Brake Switch: The scan tool displays Applied or Released. This parameter indicates the state of the brake switch circuit input. The scan tool displays Applied when you apply the vehicle brakes. The scan tool displays Released when you release the vehicle brakes.

CAM Signal Input High to Low: The scan tool displays 0-65,535 counts. The counts increment as the PCM detects the Camshaft position sensor signal voltage going from high to low.

CAM Signal Input Low to High: The scan tool displays 0-65,535 counts. The counts increment as the PCM detects the Camshaft position sensor signal voltage going from low to high.

Clutch Pedal Position Switch: The scan tool displays Depressed or Released. The scan tool displays Depressed when you apply the vehicle clutch. The scan tool displays Released when you release the clutch pedal.

Cold Start Up: The scan tool displays Yes or No. A cold start-up is when the engine coolant temperature rises above a predetermined temperature during an ignition cycle. The next ignition cycle the engine coolant temperature should be below a predetermined temperature. Also the engine coolant temperature and the intake air temperature are less than 50° C (122° F) and are within 3° C (5° F) of each other at start-up. When the above is true the scan tool displays Yes.

Commanded EGR: The scan tool displays 0-5.0 volts. The commanded EGR is the EGR pintle position commanded by the PCM.

Cruise Engaged: The scan tool displays Yes/No. When the cruise control module is enabled, the scan tool displays Yes.

Current Gear: The scan tool displays 0-4. The scan tool displays which gear the transmission is in. An illegal transmission position displays 9.

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

Cyl. Mode Misfire Index: The scan tool displays a range of 0-65,535. This parameter displays the amount of crankshaft decelerations. When an engine is operating without a misfire, the scan tool displays less than 1000 counts. When an engine misfire occurs, the counter displays more than 1000 counts.

Desired IAC Airflow: The scan tool displays a range of 0-64 grams per second (g/s). This parameter displays a calculated airflow within the IAC passage.

Desired IAC Position: The scan tool displays a range of 0-255 counts. This parameter displays the desired IAC position as requested by the PCM.

Desired EGR Position : The scan tool displays 0-100%. This parameter displays the desired position of the EGR pintle as requested by the PCM. This parameter should be very close to Actual EGR position.

Desired Idle Speed: The scan tool displays a range of 0-3,187 RPM. The PCM commands the desired idle speed. The PCM compensates for various engine loads based on engine coolant temperature in order to keep the engine at the desired speed.

DTC Set This Ignition: The scan tool displays Yes or No. This parameter indicates if a Diagnostic Trouble Code (DTC) set during the current ignition cycle.

ECT: The scan tool displays a range of -39°C to 140°C (-38°F to 284°F). The PCM applies 5.0 volts to the 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.

EGR Closed Pintle Position: The scan tool displays 0-5.0 volts. This display represents the voltage that the PCM uses to determine whether or not the EGR valve is closed. The voltage displayed will be the closed position of the EGR pintle learned by the PCM.

EGR Pintle Position: The scan tool displays 0-5.0 volts. This parameter displays the actual EGR pintle position in voltage.

Engine Load: The scan tool displays a range of 0-100%. The PCM calculates the Engine load from engine speed and MAF sensor readings. The Engine Load increases with an increase in RPM or airflow.

Engine Oil Life Remaining: The scan tool displays 0-100%. This display represents the Engine Oil Life Index that is calculated and maintained by the PCM.

Engine Run Time: The scan tool displays Hours, Minutes, Seconds. This displays the amount of engine run time for the current ignition cycle. When you cycle the ignition off, the timer resets to zero.

Engine Speed: The scan tool displays a range of 0-10,000 RPM. The 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 Canister Purge: The scan tool displays a range of 0%-100%. The PCM supplies a Pulse Width Modulated (PWM) duty cycle to control the EVAP Purge Solenoid valve. 0% indicates no purge; 100% indicates full purge.

EVAP Canister Vent Valve: The scan tool displays Venting or Not Venting. The EVAP Canister Vent Valve is normally open (venting). The PCM commands the EVAP Canister Vent Valve closed (not venting) during testing of the EVAP system.

EVAP Test Inhibit: The scan tool displays Yes/No. The scan tool displays Yes when the PCM determines that certain parameters prohibit the EVAP diagnostic from running. The scan tool displays No when the PCM determines that the EVAP diagnostic is allowed to run.

Fail Counter: The scan tool displays the number of times that a diagnostic has failed.

FT Diag Inhibit: The scan tool displays Enabled or Disabled. The scan tool displays Disabled when the PCM determines that certain parameters prohibit the Fuel Trim diagnostic from running. The scan tool displays Enabled when the PCM determines that the Fuel Trim diagnostic is allowed to run.

Fuel Level Sensor: The scan tool displays 0-5.00 volts. The scan tool displays below 1.0 volt for an empty tank, and close to 2.5 volts for a full tank.

Fuel Tank Level Remaining: The scan tool displays in Liters or Gallons the amount of fuel remaining in the fuel tank.

Fuel Tank Level Remaining: The scan tool displays 0-100%. The scan tool displays in percentage the amount of fuel remaining in the fuel tank.

Fuel Tank Pressure: The scan tool displays in -32.7 to 13.96 mm/Hg or -17.4 to 7.5 (in/H2O). This parameter indicates the pressure\vacuum inside of the fuel tank. A negative value indicates a vacuum. A positive value indicates a pressure.

Fuel Tank Pressure Sensor: The scan tool displays 0-5.0 volts. The scan tool displays in voltage the pressure inside of the fuel tank.

Fuel Tank Rated Capacity:  The scan tool displays the capacity of the fuel tank in Liters or Gallons.

Fuel Trim Cell: The scan tool displays a range of 0 to 23. The PCM determines from the 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: The scan tool displays Enabled or Disabled. When conditions are appropriate for enabling long term fuel trim corrections, the scan tool displays Enabled. This indicates that the long term fuel trim is responding to the short term fuel trim. If the scan tool displays Disabled, then long term fuel trim will not respond to changes in short term fuel trim.

Generator L Terminal: The scan tool displays Active or Inactive. The scan tool displays Inactive if the PCM does not detect a correct voltage on the L terminal circuit. The scan tool displays Active under normal operating conditions.

HO2S Bank 1 and Bank 2 Sensor 1: The scan tool displays a range of 0-1,106 mV. The HO2S Bank 1 and Bank 2 Sensor 1 parameter represents the fuel control exhaust oxygen sensor output voltage. The voltage fluctuates constantly within a range between 10 mV (lean exhaust) and 1,000 mV (rich exhaust) while operating in Closed Loop.

HO2S Bank 1 and Bank 2 Sensor 2: The scan tool displays a range of 0-1,106 mV. The HO2S Bn1 and Bn2 Sensor 2 parameter represents the exhaust oxygen sensor output voltage. The voltage fluctuates constantly within a range between 10 mV (lean exhaust) and 1,000 mV (rich exhaust) while operating in Closed Loop.

HVAC in Recirculation Mode: The scan tool displays Yes or No. This parameter displays the PCM's commanded state of the recirculation door not the HVAC controller's commanded state. Changing the state of the recirculation door, via the HVAC control head, does not affect this parameter. This parameter changes from No to Yes when the Secondary A/C High pressure switch closes for a predetermined time.

IAC Position: The scan tool displays counts from 0 to 1,024. The counts represent the commanded IAC position by the PCM. The scan tool displays 0 counts for a fully seated IAC pintle. The counts increase as the idle increases. The counts vary depending on the load placed on the engine at idle.

IAT: The scan tool displays a range of -39°C to 140°C (-38°F to 284°F). The PCM converts the resistance of the intake air temperature sensor to degrees. The PCM uses the Intake Air Temperature (IAT) in order to adjust fuel delivery and spark timing according to incoming air density.

IC Circuit Cylinder 1-8: The scan tool displays OK or Fault. If there is a problem with an ignition control circuit, the scan tool displays Fault. The scan tool displays OK under the normal operating conditions.

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

Inj. PWM Average Bank 1 and Bank 2: The scan tool displays a range of 0-1,000 millisecond (ms). The Injector average indicates the amount of time the PCM commands each injector ON during each engine cycle. A longer injector pulse width causes more fuel to be delivered. The Injector Pulse Width increases with an increased engine load.

Knock Retard: The scan tool displays a range of 0.0°-16°. Knock Retard indicates the amount of spark the PCM removes from the IC spark advance in response to the signal from the knock sensors.

Long FT1 and FT2 Average: The scan tool displays percentage. This parameter indicates the average of all long term fuel trim cells. The short term fuel trim cells are rated (weighted) for the amount of which they are used. For example, an idle cell is rated higher than a wide open cell. If a fueling malfunction occurs in the idle cell and the wide open cell, the average would be more affected by the idle cell than the wide open cell. A negative value significantly below 0% indicates that the fuel system is rich and fuel delivery is being reduced (decreased injector pulse width). A positive value significantly greater than 0% indicates that a lean condition exists and the PCM compensates by adding fuel (increased injector pulse width). When the average of the cells reach a predetermined high or low, a fuel trim DTC sets.

Long Term FT Bank 1 and Bank 2: The scan tool displays percentage. The 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% indicates that fuel delivery requires no compensation in order to maintain the PCM commanded air/fuel ratio. A negative value significantly below 0% indicates that the fuel system is rich and the PCM is reducing the fuel delivery (decreased injector pulse width). A positive value significantly greater than 0% indicates that a lean condition exists and the PCM compensates by adding fuel (increased injector pulse width). Fuel trim values at maximum authority indicates an excessively rich or lean system.

Loop Status: The scan tool displays Open or Closed. Closed Loop indicates that the 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 TP sensor, engine coolant, and MAF sensor inputs only.

Low Coolant Level: The scan tool displays Yes or No. This parameter indicates when the engine coolant level is low. The scan tool displays Yes when the PCM detects the engine coolant level is low.

Low Oil Lamp: The scan tool displays On or Off. The scan tool displays On when the PCM detects that there is a low oil level condition. The Low Oil Lamp is then commanded on by the PCM.

Low Oil Level: The scan tool displays Yes or No. This parameter indicates when the engine oil level is low. The scan tool displays Yes when the PCM detects the engine oil level is low.

MAF: The scan tool displays a range of 0.0-655 g/s. The MAF (Mass Air Flow) is the MAF input frequency converted to grams of air per second. This indicates the amount of air entering the engine.

MAF Frequency: The scan tool displays a range of 0-31,999 Hz. The MAF sensor is a hot wire type air flow sensor. The PCM converts current draw needed by the MAF (to keep the hot wires at a constant temperature) into a frequency signal. The scan tool displays this frequency in a Hertz signal.

MAP: The scan tool displays a range of 10-105 kPa and 0.00-5.0 volts. The Manifold Absolute Pressure (MAP) sensor measures the absolute pressure in the intake manifold.

MIL: The scan tool displays On or Off. The scan tool indicates if the PCM has commanded the Malfunction Indicator Light (MIL) On.

Mileage Since DTC Cleared: The scan tool displays Kilometers or Miles. This parameter indicates the mileage accumulated since an emission Diagnostic Trouble Code cleared. The PCM stores this mileage in the Freeze Frame and Failure records buffers.

Mileage Since First Failure: The scan tool displays Kilometers or Miles. This parameter indicates the mileage accumulated since an emission Diagnostic Trouble Code first failed. The PCM stores this mileage in the Freeze Frame and Failure records buffers.

Mileage Since MIL Request: The scan tool displays Kilometers or Miles. This parameter indicates the mileage accumulated since the PCM requested the MIL to illuminate. The PCM stores this mileage in the Freeze Frame and Failure records buffers.

Misfire Current Cyl. #1 - #8: The scan tool displays a range of 0-255 counts. The Misfire Current counters increment at a rate according to the number of possible misfires the 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 - #8: The scan tool displays a range of 0-65,535 counts. 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.

Misfiring Cylinder: The scan tool displays Prim. Cyl # 0-8 and Sec. Cyl # 0-8. When a multiple misfire occurs, the scan tool displays the cylinder with the most significant misfire under Prim. Cyl. The scan tool displays the least significant misfire under Sec. Cyl.

Misfire Revolution Status: The scan tool displays Reject/Accept. This parameter indicates that the misfire diagnostic is inhibited. The scan tool displays Reject when the conditions for running the DTC are not in range.

Not Run Counter: The scan tool displays counts from 0-65,535. The scan tool displays the number of times a DTC diagnostic has not reached it's predetermined criteria in order to run since it's first failure.

Pass Counter: The scan tool displays counts from 0-65,535. The scan tool displays the number of times a DTC has passed.

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.

PCM/VCM in VTD Fail Enable: The PCM displays Yes or No. The scan tool displays Yes if the BCM and the PCM loose communications with each other after the BCM sends the correct password. The scan tool displays No if the BCM is communicating the correct password to the PCM.

PRND A, B, C, P Input: The scan tool displays On or Off. The scan tool displays a combination of switch patterns to indicate the transmission shift lever position.

PRND Position: The scan tool displays the gear shift lever position.

Revolutions with Misfire: The scan tool displays the number engine revolutions the engine is misfiring.

SHRT FT1 and FT 2 Average: The scan tool displays Percentage. This parameter indicates the average of the short term fuel trim cells. The short term fuel trim cells are rated (Weighted) for the amount of which they are used. For example, the PCM rates an idle cell higher than a wide open cell. If a fueling malfunction is occurs in the idle cell and the wide open cell, the idle cell would affect more than then the wide open cell. A negative value significantly below 0% indicates that the fuel system is rich and the PCM is reducing the fuel delivery (decreased injector pulse width). A positive value significantly greater than 0% indicates that a lean condition exists and the PCM is compensating by adding fuel (increased injector pulse width). When the average of the cells reach a predetermined high or low, a fuel trim DTC sets.

Short Term FT Bank 1 and Bank 2: The scan tool displays Percentage. The Short Term Fuel Trim represents a short-term correction to fuel delivery by the 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%. The PCM adds fuel. If the oxygen sensor voltage stays mainly above the threshold, the short term fuel trim decreases below 0% 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.

Spark: The scan tool displays a range of -64° to 64°. The scan tool displays the amount of degrees the PCM commands the spark advance on the IC circuit. The PCM computes the desired spark advance using the following: (1) Engine coolant temperature; (2) Engine speed (RPM); (3) Load; (4) Vehicle speed. The PCM adjusts the timing.

Start Up ECT: The scan tool displays a range of -39°C to 140°C (-38°F to 284°F). The scan tool displays the Engine Coolant Temperature at the time the engine was started. The PCM uses Start Up ECT for certain DTCs.

TCC Duty Cycle: The scan tool displays Disabled or Enabled. This parameter is the commanded state of the TCC PWM solenoid. The scan tool displays Enabled when the commanded state of the solenoid is ON. The scan tool displays Disabled when the solenoid is OFF.

TCC Enable Solenoid: The scan tool displays Enabled or Disabled. The scan tool displays Enabled when the electrical system supplies a voltage to the TCC Enable solenoid .

Total Misfire Current Count: The scan tool displays a range of 0-255. The Total Misfire Current Count displays the total number of cylinder firing events that the PCM detected as being misfires during the last 200 crankshaft revolution sample period.

Total Misfire Failures Since First Fail: The scan tool displays a range of 0-65,535. The Total Misfire Failures Since First Fail displays the total number of cylinder firing events that the PCM detected as being misfires since the first failure.

Total Misfire Passes Since First Fail: The scan tool displays a range of 0-65,535. The Total Misfire Passes Since First Fail displays the total number of cylinder firing events that the PCM detected as being good since the first fail.

TP Angle: The scan tool displays 0-100%. The scan tool displays the amount of throttle opening in percentage. The scan tool displays about 0% at closed throttle. The scan tool displays about 100% at wide open throttle.

TP Sensor: The scan tool displays 0-5 volts. The scan tool displays the amount of throttle opening in voltage. When the throttle is at a closed throttle the voltage is between 0.4-0.9 volts. When the throttle is at wide open throttle the voltage is above 4.0 volts.

Transmission OSS: The scan tool displays a range of 0-8192 RPM. This parameter displays the rotational speed of the transmission output shaft.

Transmission Range Switch: The scan tool displays the transmission gear position.

Vehicle Speed: 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.

VTD Auto Learn Timer: The scan tool displays Active/Inactive. The auto learn timer is the indication if the VTD system is in the learn mode and has not timed out (10 minutes).

VTD Fuel Disabled: The scan tool displays Active/Inactive. If the PCM has not received the correct password from the Body Control Module (BCM), the PCM disables the fuel system and the scan tool displays Active. The scan tool displays Inactive under normal operating conditions.

VTD Fuel Disable Until Ignition Off: The scan tool displays Yes or No. With the ignition on and a VTD code present, the scan tool displays Yes.

Warm Ups w/o Emission Faults: The scan tool displays a range of 0-255. This parameter counts the number of warm up cycles without an emission fault present. The counter increments to 255 and roll 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.

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