A list of each data message displayed on the scan tool will be explained in two groups; Engine or Transmission. This information will assist in emission or driveability problems. The displays can be viewed while the vehicle is being driven. Always perform the Powertrain On-Board Diagnostic (OBD) System Check first. The OBD System Check will confirm proper system operation.

A/B/C Range Sw.-Range On On On/Off Off Off: They are used to detect which gear has been manually selected. Engine must be running. Refer to Scan Tool Data Definitions in Automatic Transmission-4L80-E.

A/C Compressor-Range engaged/disengaged: Indicates weather or not A/C compressor is engaged. The output test function in the scan tool can only activated with the key ON, and the engine OFF.

A/C Relay-Range Disabled/Enabled: Represents the commanded state of the A/C clutch control relay. The A/C clutch should be engaged with ON displayed.

A/C Request-Range ON/OFF: Represents the state of the A/C request input from the control head.

Actual EGR - Range 10-200 kPa, 0-5.0 Volts: Actual EGR vacuum going to the EGR valve.

Act. Inj. Timing-Range 0-25.0 Degrees: Current actual injection timing.

APP Angle-Range 0-100%: Computed by the PCM from APP module voltage (throttle position) and should display 0% at idle and 100% at wide open throttle.

APP 1-Range 0-5 Volts: The PCM uses the APP sensors to control fuel delivery as requested by the driver. Three APP sensors are located in a module at the base of the accelerator pedal. The PCM only requires information from one sensor, the other two serve as fail safes. APP 1 should read about 0.35-0.95 volts at idle to above 4.0 volts at wide open throttle.

APP 2-Range 0-5 Volts: The PCM uses the APP sensors to control fuel delivery as requested by the driver. Three APP sensors are located in a module at the base of the accelerator pedal. The PCM only requires information from one sensor, the other two serve as fail safes. APP 2 should read about 4.5 volts at idle and steadily decrease to about 1.0 volt at wide open throttle.

APP 3-Range 0-5 Volts: The PCM uses the APP sensors to control fuel delivery as requested by the driver. Three APP sensors are located in a module at the base of the accelerator pedal. The PCM only requires information from one sensor, the other two serve as fail safes. APP 3 should read about 4.0 volts at idle and steadily decrease to about 2.5 volts at wide open throttle.

BARO-Range 10-105 kPa, 0-5 Volts: The BARO reading is determined from the boost sensor at ignition ON, engine OFF. The BARO reading display represents barometric pressure and is used to compensate for altitude differences.

Boost Pressure-Range 10-200 kPa, 0-5.0 Volts: The amount of turbo boost pressure in the intake manifold. This is measured in kPa and volts. True boost pressure is determined by subtracting BARO from the actual reading.

Boost Solenoid-Range 0-100%: The PCM cycles the boost solenoid PWM ON and OFF. The ON time (duty cycle) of the solenoid valve is expressed as a percent. The Boost pulse width modulated solenoid meters the vacuum level at the wastegate valve actuator as commanded by the PCM.

Brake Switch-Range open/closed: When the brake pedal is applied, the switch sends a signal to the PCM to disengage the cruise control.

Calc. A/C Load-Range: The amount of load the A/C is putting on the engine.

Crank Ref. Missed-Range 0- 8: The scan tool will display the number of crank pulses missed. At idle it should read 0.

Cruise Active-Range ON/OFF: Indicates if the vehicle is in cruise control.

Cruise Brake Sw.-Range open/closed: Is used for stop lamps and a redundant cruise control disengagement switch.

Cruise Switch-Range ON/OFF: Indicates if the cruise switch (on turn signal lever) is in the ON position.

Cylinder Air - Range 0.25-1.25 g/cyl: The actual amount of air going through the MAF. The conversion of the MAF sensor readings into Grams per Cylinder (g/cyl).

Desired Cylinder Air - Range 0.25-1.25 g/cyl: The requested Cylinder Air by the PCM. This is based on engine load and speed.

Desired EGR - Range 10-200 kPa, 0-5.0 Volts: The PCM command for EGR vacuum.

Desired Idle-Range 0-3187 RPM: The idle speed that is requested by the PCM. The PCM will compensate for various engine loads based on engine coolant temperature to keep the engine at the desired speed.

Des. Inj. Timing-Range 0-25.5 Degrees: The amount of injection timing requested by the PCM.

Device Control-Range YES/NO: Indicates if the scan tool has taken control of a system under output tests.

DTC Set This Ign.-Range #: Indicates the total number of current DTCs set this ignition cycle.

ECT-Range -40°C to 151°C, -40°F to 304°F: The engine coolant temperature (ECT) sensor sends a signal to the PCM relative to engine coolant temperature. The sensor is a thermistor which changes internal resistance as temperature changes. When the sensor is cold (internal resistance high), the PCM monitors a high signal voltage and interprets it as a cold engine. As the sensor warms (internal resistance decreases), the voltage signal will decrease and the PCM will interpret the lower voltage as a warm engine.

ECT Sensor-Range 0-5 Volts: The engine coolant temperature (ECT) sensor sends a signal to the PCM relative to engine coolant temperature. The sensor is a thermistor which changes internal resistance as temperature changes. When the sensor is cold (internal resistance high), the PCM monitors a high signal voltage and interprets it as a cold engine. As the sensor warms (internal resistance decreases), the voltage signal will decrease and the PCM will interpret the lower voltage as a warm engine.

EGR Adaptive Learn Matrix - Range 0-15: The Adaptive Learn Matrix (ALM) bases itself on Mass Air Flow (MAF) to adjust the EGR control vacuum. As backpressure or other system variations increase over the life of the vehicle the ALM will trim the EGR control vacuum to compensate. The ALM has sixteen cells in which each cell covers a range of engine speed (RPM) and load (mm3).

EGR Duty Cycle-Range 0-100%: The PCM cycles the EGR solenoid PWM ON and OFF. The ON time (duty cycle) of the EGR solenoid valve is expressed as a percent. The EGR pulse width modulated solenoid meters the vacuum level at the EGR valve actuator as commanded by the PCM.

EGR Sensor - Range 0-5 Volts: The conversion of Actual EGR into a voltage.

EGR Vent Sol. - Range ON/OFF: The PCM commands the EGR vent solenoid to purge vacuum to the atmosphere when there is a desire to quickly turn off EGR flow.

Engine Load-Range 0-100%: The amount of load on the engine.

Engine Run Time-Range 00:00:00 (HRS/MIN/SEC): A measure of how long the engine has been operating. When the ignition is cycled to OFF the value is reset to zero.

Engine Speed-Range 0-9999 RPM: Engine speed is computed by the PCM from the crankshaft position sensor. If the crankshaft position sensor is inoperative, an rpm reading is taken from the injection pump cam signal. It should remain close to desired idle under various engine loads with the engine idling. Engine speed value is very accurate.

Engine Torque-Range 0-999 ft/lb: The amount of engine torque.

ESO Solenoid-Range ON/OFF: The ESO is located on the fuel injection pump. When the ignition switch is OFF, the ESO is in the NO FUEL position. It prevents fuel from entering the fuel injection pump.

4WDL Mode-Range: Indicates if vehicle is in the four wheel drive mode.

Front Axle Switch-Range Engaged/Disengaged: Indicates weather or not the front axle state is being detected by the PCM.

Fuel Rate-Range 0-80mm3: This reading is displayed in millimeters cubed (mm3). This is the amount of fuel the PCM is requesting.

Fuel Temp.-Range -28°C to 140°C, -18°F to 285°F: There is a thermistor located in the optical sensor that determines fuel temperature. When the sensor is cold (internal resistance high) the PCM monitors a high signal voltage which it interprets as low fuel temperature. As the sensor warms (internal resistance low) the voltage signal will decrease and the PCM will interpret the low voltage as warm fuel.

Glow Plug-Range 0-25.5 volts: The amount of voltage the glow plug system is drawing. The scan tool can be used to indicate if the glow plugs actually turned ON by monitoring the voltage drop. Also, a good functional check of the glow plug relay.

Glow Plug System-Range ON/OFF: Glow Plug System-Range ON/OFF Indicates whether or not the PCM has requested the glow plugs to be turned ON.

IAT-Range -40°C to 151°C, -40°F to 304°F: The intake air temperature sensor sends a signal to the PCM relative to the incoming air. The IAT is used by the PCM to adjust fuel delivery.

Ignition Volts-Range 0-25.5 volts: This represents the system voltage measured by the PCM at its ignition feed circuit. Ignition voltage is only present when the vehicle is running.

Inj. Pump Cam Reference Missed-Range 0-8: The scan tool will display the number of cam pulses missed. At idle it should read 0.

Inj. Pump Sol. Closure Time-Range 0.0-4.0 milliseconds: Indicates the amount of time the fuel solenoid takes to close. When engine load is increased, closure time will fluctuate.

Lift Pump-Range 0-25.5 volts: The amount of voltage the lift pump system is drawing. Also, a good functional check of the lift pump relay and oil pressure switch.

Lift Pump System-Range disabled/enabled: Indicates whether or not the PCM has requested the lift pump to be turned ON. This display can not be used to determine if the lift pump is actually ON.

MAF - Range 0-6553.5 g/s: The mass air flow sensor measures the amount of air entering the engine during a given time. The PCM uses this information to monitor the EGR flow rates only.

MAF Frequency - Range 0-65535 Hz: This is the conversion of MAF from grams per second (g/s) into a frequency (Hz).

MPH km/h-Range 0-98 mph: Vehicle speed is a PCM internal parameter. It is computed by timing pulses coming from the vehicle speed sensor (VSS). Vehicle speed is used in checking TCC lock-up speed or speedometer accuracy. Speed is displayed in both miles per hour (mph) and kilometers per hour (km/h).

MIL Lamp-Range ON/OFF: Represents the commanded state of the Service Engine Soon (MIL) lamp.

# of Curr. DTCs-Range #: Indicates the total number of current DTCs set. Does not necessarily mean the MIL is illuminated.

PCM in VTD Fail Enable: The scan tool display is Yes or No. This will indicate that the PCM received a good password from the Passlock module and the vehicle has started and a failure has occurred. The PCM will continue to enable fuel.

PC Solenoid-On/Off: This value is the commanded state of the pressure control solenoid. Refer to Scan Tool Data Definitions in Automatic Transmission-4L80-E.

Resume Switch-Range ON/OFF: Indicates if the cruise control resume switch is activated. The scan tool may be used to determine if the cruise control resume set switch is functioning properly.

Set Switch-Range ON/OFF: Indicates if the cruise control set switch is activated. The scan tool may be used to determine if the cruise control set switch is functioning properly.

Startup Coolant - Range -40°C to 151°C, -40°F to 304°F: A reading of the vehicles coolant temperature at startup. This will change every key cycle.

STS Lamp-Range ON/OFF: Represents the commanded state of the service throttle soon lamp.

TCC Enabled-Range disabled/enabled: Indicates if TCC is engaged.

TDC OFFSET-Range -2.50 to + 2.50 Degrees: The PCM has the ability to determine the amount of offset needed to bring the engine to top dead center. This is used by the PCM to determine proper injection timing and fuel delivery. This value may be displayed as a positive or negative number.

TFT-Range- -40°C to 151°C, -40°F to 304°F: This value represents the input signal of the transmission fluid temperature sensor. Refer to Scan Tool Data Definitions in Automatic Transmission-4L80-E.

TFT Sensor-Range 0-5 volts: This value represents the input signal of the transmission fluid temperature sensor in voltage. Refer to Scan Tool Data Definitions in Automatic Transmission-4L80-E.

TR Switch-Range Park/Neutral, Reverse, Drive 4, Drive 3, Drive 2, Low and Invalid: These values represent the decoded sequence of the transmission range pressure switch assembly circuits and are to determine manual valve position.

VTD Auto Learn Timer: The scan tool display is Active or Inactive. The auto learn timer will indicate if the Vehicle Theft Deterrent (VTD) system is in learn mode and has not timed out (10 minutes.)

VTD Fuel Disable: The scan tool display is Active or Inactive. If the PCM has not received the correct password from the Passlock module the PCM will disable fuel to the fuel system, and Active will be displayed on the scan tool.

VTD Fuel Disable Until Ign. Off: The scan tool display is Yes or No. With the ignition ON and a VTD code stored, the scan tool will display Yes.

1-2 Sol 2-3 Sol-Range On Off/On Off: These values are the command status of the 1-2 and the 2-3 shift solenoids. ON represents a commanded energized state (current flowing through solenoid). OFF represents a commanded non-energized state (current not flowing through solenoid). Refer to Scan Tool Data Definitions in Automatic Transmission-4L80-E.

Freeze Frame and Failure Record Data Definitions: A freeze frame and failure record data list consist of as many of the same parameters as in an engine data list. The list below defines the parameters not found in an engine data list.

Fail Counter-Range (decimal): The number of ignition cycles that a test has ran and failed (at least once).

First Odometer-Range miles (x16): The amount of miles (in 16 mile increments) that the vehicle has traveled since the freeze frame or failure record has been stored.

Last Odometer-Range miles (x16): Every time a failure occurs, last odometer will reset to zero. The amount miles since the last failure (in 16 mile increments).

No Results Counter: The number of ignition cycles with out a result (pass or fail).

Pass Counter-Range (decimal): The number of ignition cycles that a test has ran and passed (at least once).