Typical Scan Tool Data Values Part 3

Scan Tool Data Definitions
Not all parameters will apply to each vehicle. Use only the parameters which apply to your particular vehicle.


Inj. PWM Average Bank 1 - Range (0 - 499 ms): The Inj. PWM Avg. Bank 1 indicates the VCM commanded injector ON time, measured in milliseconds.

Inj. PWM Average Bank 2 - Range (0 - 499 ms): The Inj. PWM Avg. Bank 2 indicates the VCM commanded injector ON time, measured in milliseconds.

KS Adjust Factor - Range (-90 to 900): The knock sensor is a piezoelectric device which detects vibration due to spark knock. The VCM monitors the knock sensor signal while it performs spark advance calculations. This allows the engine to operate at maximum spark advance with out spark knock to improve driveability and fuel economy. This parameter is the number of degrees

Knock Retard - Range (0.0 - 90 degrees): The KS Retard indicates the amount of spark advance the VCM is removing in order to control spark knock.

Knock (KS) Sensor - Range (4.5 - 5.0 Volts): The scan tool indicates the current knock sensor nominal voltage detected by the VCM. This parameter is not an indication of the level of spark knock.

Knock (KS) Sensor Activity - Range (0 - 255 Counts): The knock Sensor Activity will display a randomly fluctuating number between 0 and 255 when the VCM detects spark knock. This random number will be unchanging when no knock is present.

Long Term Fuel Trim (FT) Bn 1 - Range (0 - 255 Counts): The Long Term Fuel Trim (FT) is derived from the short term fuel trim value. The VCM uses the Long Term Fuel Trim for the long-term correction of the fuel delivery. A value of 128 counts indicates that the fuel delivery requires no compensation 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, requiring decreased injector pulse width. A value above 128 counts indicates that a lean condition exists. The VCM compensates by adding fuel, increasing the injectors pulse width.

Long Term Fuel Trim (FT) Bn 1 - Range (Percentage of Compensation Required): The Long Term Fuel Trim (FT) is derived from the short term fuel trim value. The VCM uses the Long Term Fuel Trim for the long-term correction of the fuel delivery. A value of 128 counts indicates that the fuel delivery requires no compensation 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, requiring decreased injector pulse width. A value above 128 counts indicates that a lean condition exists. The VCM compensates by adding fuel, requiring increased injector pulse width. As fuel compensation is required, the difference between commanded long term fuel trim and 128 counts will be displayed as a percentage.

Long Term Fuel Trim (FT) Bn 2 - Range (0 - 255 Counts): The Long Term Fuel Trim (FT) is derived from the short term fuel trim value. The VCM uses the Long Term Fuel Trim for the long-term correction of the fuel delivery. A value of 128 counts indicates that the fuel delivery requires no compensation 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, requiring decreased injector pulse width. A value above 128 counts indicates that a lean condition exists. The VCM compensates by adding fuel, requiring increased injector pulse width.

Long Term Fuel Trim (FT) Bn 2 - Range (Percentage of Compensation Required): The Long Term Fuel Trim (FT) is derived from the short term fuel trim value. The VCM uses the Long Term Fuel Trim for the long-term correction of the fuel delivery. A value of 128 counts indicates that the fuel delivery requires no compensation 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, requiring decreased injector pulse width. A value above 128 counts indicates that a lean condition exists. The VCM compensates by adding fuel, requiring increased injector pulse width. As fuel compensation is required, the difference between commanded long term fuel trim and 128 counts will be displayed as a percentage.

Loop Status - (Open Loop/Close Loop): The Loop Status indicates when the VCM is controlling fuel delivery which is calculated using the HO2S bank 1 and 2 inputs. This is called closed loop fuel control.

During open loop, the VCM ignores the HO2S input and bases fuel delivery upon TP, engine coolant, and MAF sensor input.

MAF - Range (0 - 512 g/s): The VCM converts the Mass Air Flow sensor signal input from frequency into grams per second. The MAF indicates the amount of air entering the engine.

MAF Frequency - Range (Frequency in Hertz): The MAF produces a frequency as it measures airflow entering the engine. The VCM detects this frequency on the signal circuit and converts it into a grams per second (g/s) of airflow scale. This raw frequency can be displayed by the scan tool as it is detected by the VCM.

Manifold Absolute Pressure (MAP) - Range (10 - 104 kpa): The Manifold Absolute Pressure (MAP) sensor measures the change in intake manifold pressure caused by engine load and engine speed changes. During WOT, MAP will be maximum During decel, vacuum will be high in the intake and MAP will be displayed at its minimum pressure.

Manifold Absolute Pressure (MAP) - Range (0.0 - 5.0 Volts): The MAP sensor produces a low signal voltage when the manifold pressure is low. A low MAP voltage indicates a high vacuum in the intake manifold. The MAP sensor produces a high signal voltage when the manifold pressure is high. A high MAP voltage indicates a low vacuum in the intake manifold. With the ignition ON and the engine OFF, the manifold pressure equals the ambient atmospheric pressure. This will produce a relatively high MAP signal voltage. The VCM uses this information as an indication of the vehicle's altitude. This parameter is referred to as the BARO.

Mileage Since DTC Clear - Range (Km/Mi): The scan tool indicates the total distance the vehicle has traveled since the DTCs were cleared.


Misfire Current Cyl. #1 - #6 - Range (Current Counts): The scan tool displays the number of misfires detected during each2oo crankshaft revolution sampling period. Each cylinder has its own register to record misfires that have occurred. If the Misfire Current Cyl is incrementing, it will be reset to zero after 200 crankshaft revolutions. If the misfire DTC has set, the number of misfires in the register will be added to the Misfire History cyl register each time the current cyl. register is reset to zero.

Misfire History Cyl. #1 - #6 - Range (Counts): The scan tool displays a record of misfires that have occurred since the misfire DTC was set. This parameter will be summed with the current cylinder register each time the 200 crankshaft revolution sample is reset to zero if the current misfire test block exceeds an allowable misfire threshold.

PCM/VCM in VTD Fail Enable - (Yes/No): This parameter will indicate when the VCM detects a VTD failure after the vehicle was running. VCM in VTD Fail Enable will indicate YES if this occurs and will allow future operation of the vehicle without shutting OFF fuel when the vehicle is started. Normal conditions with no DTCs set will display this parameter as NO.
Pre HO2S - (Not Ready/Ready): The scan tool will display Not Ready until the VCM has commanded closed loop. The HO2S is then considered Ready for operation.

Post HO2S - (Not Ready/Ready): The scan tool will display Not Ready until the VCM has determined that the post HO2S is sufficiently warm for full operation.

Power Enrichment - (Active/Inactive): The Power Enrichment parameter indicates if the Power Enrichment mode is active. Power enrichment fueling is entered during high engine load operation to provide for maximum engine output.

Powertrain DTC Set - (Yes/No): The scan tool displays if a current or history powertrain DTC is set.

Purge Leak Test - (Pass/Not Run/Fail): The Purge Leak Test parameter indicates if the evaporative system leak test has Passed or Not Run/Failed.

Reference Pulse Occurred - (Yes/No): The scan tool will indicate a Yes after a CKP sensor reference pulse has been detected by the VCM.

Rich/Lean Bn 1 - (Rich/Lean): The Rich/Lean Bn 1 parameter indicates the oxygen content in the exhaust gases in bank 1. Rich indicates low oxygen content, lean indicates high oxygen content.

Rich/Lean Bn 2 - (Rich/Lean): The Rich/Lean Bn 2 parameter indicates the oxygen content in the exhaust gases in bank 2. Rich indicates low oxygen content, lean indicates high oxygen content.

Short Term Fuel Trim (FT) Bn 1 - Range (0 - 255 Counts): The short term fuel trim was formerly the fuel integrator. The short term fuel trim represents a short-term correction to the fuel delivery by the VCM in response to the amount of time the HO2S voltage spends above or below the 450 mV threshold. A HO2S voltage reading below 450 mV indicates a lean air to fuel mixture. If the HO2S voltage averages below the 450 mV threshold, the short term fuel trim counts increase in order to add fuel. If the HO2S voltage averages above the 450 mV threshold, the VCM reduces the fuel delivery in order to compensate for the indicated rich condition.

Short Term Fuel Trim (FT) Bn 1 - Range (Percentage of Compensation Required): The short term fuel trim was formerly the fuel integrator. The short term fuel trim represents a short-term correction to the fuel delivery by the VCM in response to the amount of time the HO2S voltage spends above or below the 450 mV threshold. As fuel compensation is required, the difference between commanded Short Term Fuel Trim and 128 counts will be displayed as a percentage.

Short Term Fuel Trim (FT) Bn 2 - Range (0 - 255 Counts): The short term fuel trim was formerly the fuel integrator. The short term fuel trim represents a short-term correction to the fuel delivery by the VCM in response to the amount of time the HO2S voltage spends above or below the 450 mV threshold. A HO2S voltage reading below 450 mV indicates a lean air to fuel mixture. If the HO2S voltage averages below the 450 mV threshold, the short term fuel trim counts increase in order to add fuel. If the HO2S voltage averages above the 450 mV threshold, the VCM reduces the fuel delivery in order to compensate for the indicated rich condition.

Short Term Fuel Trim (FT) Bn 2 - Range (Percentage of Compensation Required): The short term fuel trim was formerly the fuel integrator. The short term fuel trim represents a short-term correction to the fuel delivery by the VCM in response to the amount of time the HO2S voltage spends above or below the 450 mV threshold. As fuel compensation is required, the difference between commanded Short Term Fuel Trim and 128 counts will be displayed as a percentage.

Small Leak Test - (Pass/Not Run/Fail): The Small Leak Test runs immediately after the Weak Vacuum Test. The EVAP system is closed and the fuel tank vacuum is monitored by the VCM. A slow loss of vacuum rate will cause this test to fail. This test will indicate either Pass or Not Run/Failed.

Spark - Range (-96 to -255 Degrees): The Spark Advance is a display of the spark advance calculation which the VCM is provided to the Ignition Control Module. The VCM calculates the desired spark advance using data such as engine temperature, RPM, load and vehicle speed.

Spark Control - (Advance/Retard): The Spark Control parameter indicates whether the VCM is advancing or retarding spark.

Start Up ECT - Range (-0 to 215 °C (-40 to419 °F)): The VCM records the engine coolant temperature when the engine is started.

Startup IAT - Range (-40 to 151 °C (-40 to 303 °F)): The VCM records the Intake Air temperature when the engine is started.

TCC Enable - (Yes/No): The scan tool indicates whether or not the VCM commanded the TCC solenoid to an active state.

TCC Duty Cycle - Range (0 - 100%): The scan tool indicates the duty cycle that the VCM has commanded to control the TCC solenoid. The TCC solenoid is pulse width modulated to provide a determined amount of pressure, which is displayed as a percentage of the supply pressure. This provides for smooth TCC engagement.

TFP Switch A/B/C Range - (ON/OFF)(ON/OFF)(ON/OFF): The A/B/C Range parameter indicates the current state of the transmission range switch. These are pressure switches internal to the transmission.

Total Misfire Current Count- Range (0 - 255): The Total Misfire Current Count indicates the total number of cylinder firing events that the VCM detected as being misfires during the last 200 crankshaft revolution sample period. Misfire is diagnosed using crankshaft speed variations in relation with engine speed and load data.

Total Misfire Failures- Range (0 - 255): The Total Misfire Failures indicates the total number of cylinder firing events that the VCM determined as misfires during the last 200 crankshaft revolution sample.

Total Misfire Passes Since First Failure- Range (0 - 65, 535): The Total Misfire Passes Since First Fail indicates the total number of cylinder firing events that the VCM detected as being good since the misfire DTC was set.

TP Angle- Range (0 - 100%): The VCM computes the TP Angle from the TP signal voltage input. This is an indication of throttle blade angle demanded by the operator. The TP Angle should read 0 percent at idle. At 0 percent, the TP voltage will read below 0.90 volts. The TP Angle should read 100% at Wide Open Throttle.

Throttle Position (TP) Sensor - Range (0 - 5 Volts): The VCM uses the Throttle Position in order to determine the amount of throttle demanded by the operator of the vehicle. The TP sensor reads between 0.36 - 0.96 volts at idle to above 4.0 volts at Wide Open Throttle (WOT).

TR Switch - Range (One of the following P R N D4 D3 D2 D1): The Trans Range (TR) Switch indicates the Trans Range selected by the operator.

Valid Ref. Pulse Occurred- (Yes/No): The scan tool will indicate YES after 2 or more CKP sensor reference pulses have been detected by the VCM.

Vehicle Speed - km/h- Range (0 - 255): The Vehicle Speed parameter indicates in MPH or km/h how fast the drive wheels are turning.

VTD Auto Learn Timer - (Active/Inactive): The Auto Learn Timer will indicate if the Vehicle Theft Deterrent (VTD) system is currently in the auto learn Mode. The auto learn mode requires approximately 10 minutes to complete.

VTD Fuel Disable - (Active/Inactive): If the VCM has not received the correct password from the Passlock Module or Body Control Module (if equipped), the VCM will disable fuel to the fuel system. If this occurs, the scan tool will display Active.

VTD Fuel Disable Until Ign OFF - (Yes/No): With the ignition ON and a VTD code stored, the scan tool will display Yes.

Weak Vacuum Test - (Pass/Not Run/Fail): The Weak Vacuum Test will run only if the Loaded Canister Test does not pass. Insufficient vacuum in the evaporative system will cause this test to fail. The two states of this parameter are Pass and Not Run/Fail.