For 1990-2009 cars

The Scan Tool Data Definitions list contains a brief description of all of the engine related parameters that are available on the scan tool. The list is arranged in alphabetical order. A given parameter may appear in any one of the data lists, and 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. The Transmission data list, the typical values and the data definitions are covered in General Information/On-Vehicle Service in Transmission.

A/C Load Signal -- Scan tool displays: Heavy/Normal: This parameter will change state when the A/C compressor system is under an excessive load during, for example, any high ambient conditions. If the system pressure exceeds 1200 kPa, the ECM will detect this pressure via the A/C load switch and increase the idle speed by about 50 RPM in order to compensate for the excess load.
A/C Compressor Control: Scan tool displays: A/C On/A/C Off: This display indicates that the ECM commands the A/C off when the engine temperature exceeds a predetermined threshold, or a heavy accel maneuver has been initiated.
A/C Request -- Scan tool displays: Yes/No: This parameter indicates that the A/C has been requested and therefore the idle air, as commanded by the ECM, has been increased.
Actual MAF at Idle: Scan tool displays: 0.0-35.4 g/s: This parameter indicates the quantity of the air flowing into the engine during the idling conditions.
Avg. Inj. Pulse at Idle: Scan tool displays: 0.0-6.1 ms: This parameter indicates the average injector pulse width of both bank 1 and bank 2 injectors during the idling conditions.
Battery Voltage: Scan tool displays: 0.0-24.0 Volts: This parameter is the battery voltage at the ECM.
Calc. Converter Temperature: Scan tool displays: 0.0-1020.0°C: This parameter is a calculated catalyst temperature and is used for catalyst monitoring as well as disabling the HO2S heaters at temperatures exceeding 800°C in order to prevent damage.
Calculated Full Pos.: Scan tool displays: Active/Inactive: This parameter indicates that all full load maps are used (for example, the fuel enrichment and the ignition).
Calculated Idle Pos.: Scan tool displays: Active/Inactive: This parameter indicates that all idle maps are used (for example, the injection, the spark advance, and the idle air control).
Calucated Torque Reduction: Scan tool displays: 0-255 steps: This parameter represents the number of steps for the requested engine torque reduction (torque management).
Cam Signal Present: Scan tool displays: Low/High: This parameter indicates the presence of a CMP sensor signal. The value toggles Low to High with each transition of the CMP signal. Due to the refresh rate of the scan tool display, and the rapid changes in the signal state, this parameter may appear to freeze occasionally when the engine is running.
Compensation Gradient: Scan tool displays: 0.0-9.18 inches of H20: This parameter indicates the measured rise in the tank pressure when the EVAP Purge valve and the EVAP Vent valve are closed.
Desired MAF at Idle: Scan tool displays: 0.0-35.4 g/s: This parameter indicates the calculated quantity of the air flowing into the engine during the idling conditions. The calculated quantity of air flowing into the engine is based on the engine load and the engine speed (RPM).
Desired Idle Speed: Scan tool displays: 0-2,550 RPM: This display shows the idle speed that is commanded by the ECM. The ECM will compensate for various engine loads in order to keep the engine close to the desired idle speed.
ECT: Scan tool displays: -48°C-143°C: This display shows the temperature of the engine coolant.
ECT Sensor: Scan tool displays: 0.3-4.9 Volts: This parameter is the actual voltage on the ECT signal circuit as measured by the ECM.
Engine Load Signal: Scan tool displays: 0-12.75 ms: This is a calculated value that changes in proportion to the amount of the load on the engine.
Engine Speed: Scan tool displays: 0-10,200 RPM: This is essentially a digital tachometer display.
EVAP Canister Vent Valve: Scan tool displays: Active/Inactive: When the EVAP diagnostic is executed, this parameter changes state from inactive to active, indicating that the EVAP Canister Vent Valve is closed.
EVAP Leakage Factor: Scan tool displays: 0-1.992: This parameter indicates the level of the canister loading, and is used by the EVAP diagnostic to either enable or disable the on board test.
EVAP Purge Valve: Scan tool displays: 0-100 percent: The ECM controls the EVAP Purge valve by using the Pulse Width Modulation (PWM). The display is the commanded pulse width (duty cycle) of the control circuit.
EVAP System Ready: Scan tool displays: No/Yes: This parameter indicates that the EVAP diagnostic test has been performed at least once.
Fuel Level Output: Scan tool displays: 0-10.1 Volts: This parameter indicates the fuel level that is measured in volts in the fuel tank. Zero volts indicates near full while 10.1 volts indicates near empty.
Fuel Pump Relay: Scan tool displays: Off/On: The ECM enables the fuel pump when the CKP sensor pulses are detected.
Fuel Tank Pressure: Scan tool displays: -11.8-11.7 inches of H2O: This sensor is used in order to monitor the pressure within the EVAP system (which includes the fuel tank). The Fuel Tank Pressure sensor is very sensitive to changes in pressure. Inches of water is a very small unit of pressure measurement. One inch of H2O equals approximately 0.25 kPa.
Fuel Tank Pressure: Scan tool displays: 0-5 Volts: This parameter is the actual voltage on the Fuel Tank Pressure sensor signal circuit as measured by the ECM.
HO2S Bank 1 Sensor 1: Scan tool displays: -406-1,124 mV: This parameter is the actual voltage on the HO2S signal circuit as measured by the ECM.
HO2S Bank 1 Sensor 2: Scan tool displays: -406-1,124 mV: This parameter is the actual voltage on the HO2S signal circuit as measured by the ECM.
HO2S Bank 2 Sensor 1: Scan tool displays: -406-1,124 mV: This parameter is the actual voltage on the HO2S signal circuit as measured by the ECM.
HO2S Bank 2 Sensor 2: Scan tool displays: -406-1,124 mV: This parameter is the actual voltage on the HO2S signal circuit as measured by the ECM.
HO2S Bn 1 & Bn 2 Ready: Scan tool displays: No/Yes: This parameter indicates that the HO2S Bn 1 & Bn 2 diagnostic tests have been performed at least once.
HO2S Heaters Ready: Scan tool displays: No/Yes: This parameter indicates that the HO2S Heaters Bn1& Bn2 diagnostic tests have been performed at least once.
HO2S Status Bank 1: Scan tool displays: Lean/Rich: When the HO2S voltage swings low, the Lean is indicated. The High signal voltage is indicated as Rich. When the sensor is active, this parameter will toggle rapidly. This parameter applies to the front (pre-catalyst) sensor.
HO2S Status Bank 2: Scan tool displays: Lean/Rich: When the HO2S voltage swings low, the Lean is indicated. The High signal voltage is indicated as Rich. When the sensor is active, this parameter will toggle rapidly. This parameter applies to the front (pre-catalyst) sensor.
IAC Long Term Air Trim: Scan tool displays: -100-100 percent: The ECM maintains the idle speed as close to the Desired Idle Speed as possible. Adjustments that are made by the ECM to compensate for the changes in the idle speed will be indicated by the Long and Short Term Air Trim values. The Short Term Air Trim values change rapidly in response to any minor fluctuations in the idle speed. These changes fine tune the idle RPM. The Long Term Air Trim values change in response to the trends in the Short Term Air Trim. The Long Term Air Trim makes coarse adjustments to the idle speed in order to re-center and restore control to the Short Term Air Trim. The Short and Long Term Air Trim can be monitored with a scan tool. The Ideal Air trim values are around 0 percent. A positive Air Trim value indicates that the ECM is adding Air (via the IAC valve) in order to compensate for a low idle speed condition. A negative Air Trim value indicates that the ECM is reducing the amount of Air in order to compensate for a high idle speed.
IAC Pulse Ratio - Scan tool displays: 0-65 percent: The ECM controls the IAC valve via two control circuits, one to drive the valve open and the other to drive the valve closed. The ECM Pulse Width Modulates both of the control circuits simultaneously. The ratio of the frequency between the two PWM signals determines the direction and the amount that the drive unit rotates the shutter within the valve.
IAC Short Term Air Trim: Scan tool displays: -100-100 percent: The ECM maintains the idle speed as close to the Desired Idle Speed as possible. The adjustments that are made by the ECM in order to compensate for changes in the idle speed will be indicated by the Long and Short Term Air Trim values. The Short Term Air Trim values change rapidly in response to the minor fluctuations in the idle speed. These changes fine tune the idle RPM. The Long Term Air Trim values change in response to the trends in the Short Term Air Trim. The Long Term Air Trim makes coarse adjustments to the idle speed in order to re-center and restore control to the Short Term Air Trim. The Short Term Air Trim and the Long Term Air Trim can be monitored with a scan tool. The ideal Air trim values are approximately 0 percent. A positive Air Trim value indicates that the ECM is adding Air (via the IAC valve) in order to compensate for a low idle speed condition. A negative Air Trim value indicates that the ECM is reducing the amount of Air in order to compensate for a high idle speed.
IAT: Scan tool displays: -48°C-143°C: This display shows the temperature of the air entering the air induction system. The temperature should be close to ambient, however, high underhood temperatures and low vehicle speed may cause the IAT to climb.
IAT Sensor: Scan tool displays: 0.3-4.9 Volts: This voltage is the actual voltage on the IAT signal circuit to the ECM as measured by the ECM.
Ignition Coil 1 & 4: Scan tool displays: Active/Inactive: This parameter indicates ECM control of the primary side ignition circuit . The value toggles Active to Inactive with each control command that is issued by the ECM. Due to the refresh rate of the scan tool display, and the rapid changes in the signal state, this parameter may appear to freeze occasionally when the engine is running.
Ignition Coil 2 & 5: Scan tool displays: Active/Inactive: This parameter indicates ECM control of the primary side ignition circuit . The value toggles Active to Inactive with each control command that is issued by the ECM. Due to the refresh rate of the scan tool display, and the rapid changes in the signal state, this parameter may appear to freeze occasionally when the engine is running.
Ignition Coil 3 & 6: Scan tool displays: Active/Inactive: This parameter indicates ECM control of the primary side ignition circuit . The value toggles Active to Inactive with each control command issued by the ECM. Due to the refresh rate of the scan tool display, and the rapid changes in the signal state, this parameter may appear to freeze occasionally when the engine is running.
Int. Plenum Sw. Valve: Scan tool displays: Open/Closed: This parameter indicates the commanded position of the Intake Plenum Switchover valve which is part of the Multi-Ram System.
Int. Reson. Sw. Valve: Scan tool displays: Open/Closed: This parameter indicates the commanded position of the Intake Resonance Switchover valve which is part of the Multi-Ram System.
Knock Signal Present: Scan tool displays: No/Yes: The engine spark knock (pre-ignition) will cause Yes to be displayed. Some types of internal mechanical noise may also be interpreted as a spark knock.
Knock Retard: Scan tool displays: 0-191 degrees: The ECM will retard the ignition timing in order to the reduce spark knock. This system can retard timing on a per cylinder basis. When spark knock is detected, the ECM uses the CKP and CMP sensor signals in order to determine which cylinder(s) is affected.
Lean/Rich Avg. Bn 1: Scan tool displays: 0-655 secs: This parameter indicates the average time that it takes for the HO2S Bn 1 to switch from lean to rich.
Lean/Rich Avg. Bn 2: Scan tool displays: 0-655 secs: This parameter indicates the average time that it takes for the HO2S Bn 2 to switch from lean to rich.
Long Term Add. FT Bn 1: Scan tool displays: -2.05-2.05 ms: A change made to the fuel delivery will be indicated by the Long and Short Term Fuel Trim values. The Short Term Fuel Trim values change rapidly in response to the HO2S signal voltages. These changes fine tune the engine fueling. The Long Term Fuel Trim values change in response to trends in the Short Term Fuel Trim. The Long Term Fuel Trim makes coarse adjustments to the fueling in order to re-center and restore the control to the Short Term Fuel Trim. The Short and Long Term Fuel Trim can be monitored with a scan tool. Ideal fuel trim values are approximately 0 percent for the Long Term Mul. FT and the Short Term FT and approximately 0.0 milliseconds. A positive Fuel Trim value indicates that the ECM is adding the fuel in order to compensate for a lean condition. A negative Fuel Trim value indicates that the ECM is reducing the amount of fuel in order to compensate for a rich condition.
Long Term Add. FT Bn 2: Scan tool displays: -2.05-2.05 ms: A change made to the fuel delivery will be indicated by the Long and Short Term Fuel Trim values. The Short Term Fuel Trim values change rapidly in response to the HO2S signal voltages. These changes fine tune the engine fueling. The Long Term Fuel Trim values change in response to the trends in the Short Term Fuel Trim. The Long Term Fuel Trim makes coarse adjustments to the fueling in order to re-center and restore control to the Short Term Fuel Trim. The Short Term Fuel Trim and the Long Term Fuel Trim can be monitored with a scan tool. Ideal fuel trim values are approximately 0 percent for the Long Term Mul. FT and Short Term FT and approximately 0.0 milliseconds. A positive Fuel Trim value indicates that the ECM is adding fuel in order to compensate for a lean condition. A negative Fuel Trim value indicates that the ECM is reducing the amount of fuel in order to compensate for a rich condition.
Long Term Mult. FT Bn 1: Scan tool displays: -100-100 percent: A change made to the fuel delivery will be indicated by the Long Term Fuel Trim values and the Short Term Fuel Trim values. The Short Term Fuel Trim values change rapidly in response to the HO2S signal voltages. These changes fine tune the engine fueling. The Long Term Fuel Trim values change in response to the trends in the Short Term Fuel Trim. The Long Term Fuel Trim makes coarse adjustments to the fueling in order to re-center and restore control to the Short Term Fuel Trim. The Short Term Fuel Trim and the Long Term Fuel Trim can be monitored with a scan tool. Ideal fuel trim values are approximately 0 percent for Long Term Mul. FT and Short Term FT and approximately 0.0 milliseconds. A positive Fuel Trim value indicates that the ECM is adding fuel in order to compensate for a lean condition. A negative Fuel Trim value indicates that the ECM is reducing the amount of fuel in order to compensate for a rich condition.
Long Term Mult. FT Bn 2: Scan tool displays: -100-100 percent: A change made to the fuel delivery will be indicated by the Long Term Fuel Trim values and the Short Term Fuel Trim values. The Short Term Fuel Trim values change rapidly in response to the HO2S signal voltages. These changes fine tune the engine fueling. The Long Term Fuel Trim values change in response to the trends in the Short Term Fuel Trim. The Long Term Fuel Trim makes coarse adjustments to fueling in order to re-center and restore control to the Short Term Fuel Trim. The Short Term Fuel Trim and the Long Term Fuel Trim can be monitored with a scan tool. Ideal fuel trim values are approximately 0 percent for Long Term Mul. FT and Short Term FT and approximately 0.0 milliseconds. A positive Fuel Trim value indicates that the ECM is adding fuel in order to compensate for a lean condition. A negative Fuel Trim value indicates that the ECM is reducing the amount of fuel in order to compensate for a rich condition.
Loop Status Bank 1: Scan tool displays: Open/Closed: A Closed Loop operation displayed indicates that the ECM is controlling the fuel delivery according to the oxygen sensor voltage. In an Open Loop operation, the ECM ignores the oxygen sensor voltage and bases the amount of the fuel to be delivered on other input sensors. The Closed Loop operation should begin when the oxygen sensor becomes active, the engine coolant temperature exceeds 5°C (41°F) for more than 30 seconds and the ECM has seen a RPM of 1200 or greater for 10 seconds. At extremely high ambient temperatures or when towing a trailer, it is possible for the system to remain in an Open Loop operation in order to control the catalytic converter temperatures.
Loop Status Bank 2: Scan tool displays: Open/Closed: A Closed Loop operation displayed indicates that the ECM is controlling the fuel delivery according to the oxygen sensor voltage. In an Open Loop operation, the ECM ignores the oxygen sensor voltage and bases the amount of the fuel to be delivered on other input sensors. A Closed Loop operation should begin when the oxygen sensor becomes active, the engine coolant temperature exceeds 5°C (41°F) for more than 30 seconds and the ECM has seen a RPM of 1200 or greater for 10 seconds. At extremely high ambient temperatures or when towing a trailer, it is possible for the system to remain in an Open Loop operation in order to control the catalytic converter temperatures.
MAF: Scan tool displays: 0-5.5 Volts: The MAF sensor converts the air flow into an analog voltage signal read by the ECM.
MIL: Scan tool displays: Off/On: This display indicates the commanded state of the Malfunction Indicator Lamp (MIL). If the MIL and the display do not agree, go to the MIL Diagnosis table.
MIL Request: Scan tool displays: Active/Inactive: The TCM has no direct control of the engine MIL, but if a transmission fault occurs that is emissions related, the engine MIL must illuminate. A MIL Request circuit between the ECM and the TCM provides a means for illuminating the MIL, even though the fault was detected by the TCM. This parameter indicates the state of this circuit. An Active indicates that the signal voltage is low, an Inactive indicates that the signal voltage is high as detected by the ECM.
Misfire Current Cyl. #1: Scan tool displays: 0-255 counts: The display shows the number of misfires that have been detected during the last 200 cylinder firing events. The counters may normally display some activity, but the activity should be nearly equal for all of the cylinders, and in low numbers.
Misfire Current Cyl. #2: Scan tool displays: 0-255 counts: This display shows the number of misfires that were detected during the last 200 cylinder firing events. The counters may normally display some activity, but the activity should be nearly equal for all of the cylinders, and in low numbers.
Misfire Current Cyl. #3: Scan tool displays: 0-255 counts: This display shows the number of misfires that were detected during the last 200 cylinder firing events. The counters may normally display some activity, but the activity should be nearly equal for all of the cylinders, and in low numbers.
Misfire Current Cyl. #4: Scan tool displays: 0-255 counts: This display shows the number of misfires that were detected during the last 200 cylinder firing events. The counters may normally display some activity, but the activity should be nearly equal for all of the cylinders, and in low numbers.
Misfire Current Cyl. #5: Scan tool displays: 0-255 counts: This display shows the number of misfires that were detected during the last 200 cylinder firing events. The counters may normally display some activity, but the activity should be nearly equal for all of the cylinders, and in low numbers.
Misfire Current Cyl. #6: Scan tool displays: 0-255 counts: This display shows the number of misfires that were detected during the last 200 cylinder firing events. The counters may normally display some activity, but the activity should be nearly equal for all of the cylinders, and in low numbers.
Number of DTCs: Scan tool displays: This display indicates the actual quantity of the DTCs that are stored in the ECM.
Park/Neutral Switch: Scan tool displays: P-N or R-D-3-2-1: The P/N switch position is sent to the ECM from the TCM.
Sec. AIR Pump Relay: Scan tool displays: Active/Inactive: This display indicates the commanded state of the Secondary AIR Pump relay.
Sec. AIR System Ready: Scan tool displays: No/Yes: This parameter indicates that the Sec. AIR System diagnostic test has been performed at least once.
Short Term FT Bank 1: Scan tool displays: -100-100 percent: A change made to the fuel delivery will be indicated by the Long Term Fuel Trim values and the Short Term Fuel Trim values. The Short Term Fuel Trim values change rapidly in response to the HO2S signal voltages. These changes fine tune the engine fueling. The Long Term Fuel Trim values change in response to the trends in the Short Term Fuel Trim. The Long Term Fuel Trim makes coarse adjustments to the fueling in order to re-center and restore control to the Short Term Fuel Trim. The Short Term Fuel Trim and the Long Term Fuel Trim can be monitored with a scan tool. Ideal fuel trim values are approximately 0 percent. A positive Fuel Trim value indicates that the ECM is adding fuel in order to compensate for a lean condition. A negative Fuel Trim value indicates that the ECM is reducing the amount of fuel in order to compensate for a rich condition.
Short Term FT Bank 2: Scan tool displays: -100-100 percent: A change made to fuel delivery will be indicated by the Long Term Fuel Trim values and the Short Term Fuel Trim values. The Short Term Fuel Trim values change rapidly in response to the HO2S signal voltages. These changes fine tune the engine fueling. The Long Term Fuel Trim values change in response to the trends in the Short Term Fuel Trim. The Long Term Fuel Trim makes coarse adjustments to the fueling in order to re-center and restore control to the Short Term Fuel Trim. The Short Term Fuel Trim and the Long Term Fuel Trim can be monitored with a scan tool. Ideal fuel trim values are approximately 0 percent. A positive Fuel Trim value indicates that the ECM is adding fuel in order to compensate for a lean condition. A negative Fuel Trim value indicates that the ECM is reducing the amount of fuel in order to compensate for a rich condition.
Spark: Scan tool displays: -133 to 78 degrees CA: This is the amount of spark advance that is commanded by the ECM. A positive value indicates that the timing is advanced, and a negative value indicates that the timing is being retarded.
TC Torque Request: Scan tool displays: 0-100 percent: This parameter represents the requested engine torque (torque management) from the ABS/TC module.
TCM Torque Reduction Request: Scan tool displays: 0-100 percent: This parameter represents the spark advance requested, during shifting, from the Transmission Control module (torque management).
TCM Torque Reduction Request: Scan tool displays: No/Yes: Indicates whether any torque reduction is being requested.
Theft Deterrent Status: Scan tool displays: No Signal/Correct Code/Incorrect Code: This parameter indicates the status of the Theft Deterrent System. The Correct Code must be displayed in order for the vehicle to start.
TP Normalized: Scan tool displays: 0-100 percent: This parameter is the TP sensor voltage signal that is re-scaled to the percentage of throttle opening and Normalized (meaning, re-zeroed to the learned closed throttle position). This value should indicate 0 percent at closed throttle and close to 78 percent at WOT.
TP Sensor: Scan tool displays: 0-5.0 Volts: This parameter is the actual voltage on the TP sensor signal circuit as measured by the ECM.
TP Signal: Scan tool displays: 0-100 percent: This parameter is the actual voltage signal that is re-scaled to percent throttle opening. This value will typically not drop completely to zero at a closed throttle or reach 90 percent at a WOT, due to variations in the operating voltage range of the sensor.
Traction Control: Scan tool displays: Active/Inactive: This parameter indicates that DTC P1740 is set. This parameter is related to the ABS/TC circuit to the ECM.
Traction Control Status: Scan tool displays: Active/Inactive: This parameter indicates whether or not Traction Control is engaged.
TCM Torque Reduction Request Status: Scan tool displays: No/Yes: The TCM sends a signal to the ECM requesting a reduced engine torque during transmission shift events in order to improve the shift feel. This display indicates whether a reduced engine torque is being requested.
TWC Bn 1 & Bn 2 Ready: Scan tool displays: No/Yes: This parameter indicates that the catalytic converter diagnostic test has been performed at least once.
Vacuum Decay Gradient: Scan tool displays: 0-9.18 inches of H2O: This parameter indicates the rate of vacuum decay detected during the EVAP system diagnostic.
Vehicle Speed: Scan tool displays: 0-198 mph: A processed wheel speed sensor signal is sent to the ECM from the ABS controller. The ECM calculates the vehicle speed from this signal.
Vehicle Speed Pulse: Scan tool displays: Active/Inactive: This parameter indicates that a vehicle speed pulse was issued.