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

4WD Low Signal: This parameter displays the state of the transfer case based on the signal from the four wheel drive (4WD) low switch. The scan tool will display Enabled or Disabled. Enabled indicates the transfer case is in 4WD low gear and the 4WD low switch is closed, completing the low signal circuit. Disabled indicates the transfer case is not in 4WD low gear and the 4WD low switch is open.

4WD Signal: This parameter displays the state of the transfer case based on the signal from the front axle indicator switch. The scan tool will display Enabled or Disabled. Enabled indicates the front axle is locked in four wheel drive and the front axle indicator switch is closed, supplying voltage to the controller on the axle switch signal circuit. Disabled indicates the transfer case is not in four wheel drive and the front axle indicator switch is open.

5 Volts Reference 1: This parameter displays the voltage sensed on the 5-volt reference 1 circuit at the control module. The scan tool will display a higher value at higher voltage. The scan tool will display a lower value at lower voltage.

5 Volts Reference 2: This parameter displays the voltage sensed on the 5-volt reference 2 circuit at the control module. The scan tool will display a higher value at higher voltage. the scan tool will display a lower value at lower voltage.

5 Volts Reference 3: This parameter displays the voltage sensed on the 5-volt reference 3 circuit at the control module. The scan tool will display a higher value at higher voltage. the scan tool will display a lower value at lower voltage.

A/C Clutch Feedback Signal: This parameter displays the state of the air conditioning (A/C) compressor clutch based on the signal from the switched side of the A/C clutch relay. The scan tool will display Relay On or Relay Off. Relay On indicates the A/C clutch relay has closed, allowing voltage to the A/C compressor clutch. Relay Off indicates the A/C clutch relay is open and the A/C compressor clutch is not engaged.

A/C High Side Pressure Sensor: This parameter displays the voltage signal sent to the control module from the A/C high side pressure sensor. The A/C high side pressure sensor has a range of values indicating a low refrigerant pressure when the voltage is low to a high refrigerant pressure when the voltage is high.

A/C Relay Command: This parameter displays the commanded state of the air conditioning (A/C) clutch relay control circuit. The scan tool will display ON or OFF. ON indicates the A/C clutch relay control circuit is being grounded by the control module, allowing voltage to the A/C compressor clutch. OFF indicates the A/C clutch relay is not being commanded on by the control module.

A/C Request Signal: This parameter displays the state of the air conditioning (A/C) request input to the control module from the heating, ventilation, and air conditioning (HVAC) controls. The scan tool will display Yes or No. Yes indicates the control module is receiving a request from the HVAC system to ground the A/C clutch relay control circuit, engaging the A/C compressor clutch. No indicates the control module is not receiving a request from the HVAC system to ground the A/C clutch relay control circuit.

A/C Sec. High Pressure Switch: This parameter displays the state of the air conditioning (A/C) secondary high pressure switch as determined by the control module. The scan tool will display Open or Closed. Open indicates the A/C refrigerant pressure is not too high to operate the air conditioning. Closed indicates the refrigerant pressure is abnormally high and has closed the A/C secondary high pressure switch.

Actual Fuel Rail Pressure: This parameter displays the fuel rail pressure as calculated by the control module using the signal from the fuel rail pressure (FRP) sensor. The actual fuel rail pressure is a range of values indicating a low pressure when the fuel rail pressure is low to a high pressure when the fuel rail pressure is high. This value is listed in MPa or psi.

APP Indicated Angle: This parameter displays the angle of the accelerator pedal as calculated by the control module using the signals from the accelerator pedal position sensors. The APP indicated angle is a range of values indicating a low percentage when the accelerator pedal is not depressed to a high percentage when the accelerator pedal is fully depressed.

APP Sensor 1: This parameter displays the voltage signal sent to the control module from accelerator pedal position (APP) sensor 1 of the APP sensor assembly. APP sensor 1 is a range of values indicating a low voltage when the accelerator pedal is not depressed to a high voltage when the accelerator pedal is fully depressed.

APP Sensor 2: This parameter displays the voltage signal sent to the control module from accelerator pedal position (APP) sensor 2 of the APP sensor assembly. APP sensor 2 is a range of values indicating a low voltage when the accelerator pedal is not depressed to a high voltage when the accelerator pedal is fully depressed.

APP Sensor 3: This parameter displays the voltage signal sent to the control module from accelerator pedal position (APP) sensor 3 of the APP sensor assembly. APP sensor 3 is a range of values indicating a high voltage when the accelerator pedal is not depressed to a low voltage when the accelerator pedal is fully depressed.

Balancing Rate Cyl. 1-8: These parameter display the adjustment in fuel volume for each cylinder as calculated by the control module. The scan tool will display a negative balancing rate if the fuel volume is lowered. The scan tool will display a positive balancing rate if the fuel volume is increased.

BARO: This parameter displays the barometric pressure as calculated by the control module using the signal from the barometric pressure (BARO) sensor.

Battery Voltage: This parameter displays the voltage measured at the battery circuit of the control module. Voltage is applied to the control module from the battery at all times. The scan tool will display a low value when sensed battery voltage is low, and a high value when sensed battery voltage is high.

Boost Pressure Sensor: This parameter indicates the turbocharger boost pressure inside the engine as calculated by the control module based on the signal from the Boost pressure sensor. The scan tool will display a higher value under heavy load, and a lower value at idle.

Calculated Fuel Rate: This parameter displays the fuel rate of the fuel injection pump as calculated by the control module.

Cam Reference Signal Missed: The scan tool will display the number of cam pulses missed. The scan tool should read 0. This number will only increase due to an intermittent condition. If the signal is missing for a longer period, this parameter will remain 0.

CAM Signal Present: This parameter displays the state of the CAM signal as determined by the control module. The scan tool will display Yes if the CAM signal is being received by the control module. The scan tool will display No if the CAM signal is missing.

Check Trans Lamp: This parameter displays the commanded state of the check trans lamp control circuit. The check trans lamp should be on when the scan tool indicates the check trans lamp is commanded ON. The check trans lamp should be off when the scan tool indicates the check trans lamp is commanded OFF. The control module will command the check trans lamp On when the ignition is ON with the engine OFF in order to perform a bulb check.

CKP Sensor Pulses Missed: This parameter displays an incrementing counter when the control module does not receive a crankshaft position (CKP) sensor signal. The scan tool should read 0. This number will only increase due to an intermittent condition. If the signal is missing for a longer period, this parameter will remain 0.

Clutch Pedal Switch: This parameter displays the current state of the clutch pedal as determined by the control module. The scan tool will display Applied when the clutch pedal is depressed, and released when the clutch pedal is not depressed.

Cruise Control Active: This parameter displays the status of the cruise control system as determined by the control module. The scan tool will display Yes when the cruise control system is in control of vehicle speed. The scan tool will display No when the cruise control system is not operating.

Cruise On/Off Switch: This parameter displays the state of the on/off switch input to the control module . The scan tool will display On when the cruise ON/OFF switch is on. The scan tool will display OFF when the cruise ON/OFF switch is OFF.

Cruise Resume/Accel Switch: This parameter displays the state of the Resume/Accel switch input to the control module When the cruise control switch is in the on position and the Resume/Accel switch is activated, the scan tool displays On. When the Resume/Accel switch is released the scan tool displays Off.

Cruise Set/Coast Switch: This parameter displays the state of the Set/Coast switch input to the control module from the cruise control system. When the cruise control switch is in the on position and the Set/Coast switch is activated, the scan tool displays On. When the Set/Coast switch is released the scan tool displays Off.

Crank Signal Present: This parameter displays the state of the CKP signal as determined by the control module. The scan tool will display Yes if the CKP signal is being received by the control module. The scan tool will display No if the CKP signal is missing.

Desired EGR Position: This parameter displays the position of the exhaust gas recirculation (EGR) valve commanded by the control module. The scan tool will display 0 percent when the control module is commanding the EGR valve closed. The scan tool will display a higher percentage when the EGR valve is commanded open.

Desired FRP Regulator: This parameter displays the desired current draw of the fuel rail pressure (FRP) regulator as calculated by the control module. The scan tool will display a low value if the regulator is commanded open, and a higher value when the regulator is commanded closed.

Desired Fuel Rail Pressure: This parameter displays the desired fuel rail pressure as calculated by the control module. This value is calculated based on engine speed, engine load, and sensor inputs. The scan tool will display a higher value at higher engine speeds and loads, and a lower value at idle.

Desired Idle Speed: This parameter displays the engine idle speed in RPM as commanded by the control module. The control module compensates for various engine loads in order to maintain the desired engine speed at idle. This parameter is not valid unless the engine is running.

Desired TC Vane Position: This parameter displays the position of the turbocharger vane position sensor as the turbocharger vane position is commanded by the control module. The scan tool will display 0 percent when the control module is commanding the vanes open. The scan tool will display a higher percentage when the vanes are commanded closed.

Des. TC Vane Pos. Ctrl. Solenoid: This parameter displays the desired current draw of the turbocharger vane position control solenoid valve as calculated by the control module. The scan tool will display a high value if the solenoid is commanded open, and a lower value when the solenoid is commanded closed.

DTC Set This Ignition: This parameter displays if a diagnostic trouble code (DTC) set during the current ignition cycle.

ECT Sensor: This parameter displays the temperature of the engine coolant based on the input from the engine coolant temperature sensor. When the coolant temperature is low, the scan tool will display a low temperature. When the coolant temperature is high, the scan tool will display a high temperature.

EGR Learned Minimum Position: This parameter displays the learned minimum position of the EGR valve as calculated by the control module. The scan tool will display 0 percent if the current closed EGR position is the same as the last ignition cycle. The scan tool will display a higher value if the EGR valve has closed at a new position.

EGR Position Sensor: This parameter displays the voltage signal received from the exhaust gas recirculation (EGR) valve position sensor by the control module. The scan tool will display a lower value when the EGR valve is closed, and a higher value when the EGR valve is open.

EGR Position Sensor: This parameter displays EGR valve position as calculated by the control module based on an input from the exhaust gas recirculation (EGR) valve position sensor. The scan tool will display a lower value when the EGR valve is closed, and a higher value when the EGR valve is open.

EGR Position Variance: This parameter displays the difference between the desired EGR valve position calculated by the control module and the actual EGR position input from the EGR valve position sensor. The scan tool will display a higher value if the difference is large, and a lower value if the difference is small.

EGR Solenoid Command: This parameter displays the duty cycle commanded by the control module for the EGR valve. The scan tool will display a high percentage when the EGR valve is commanded open. The scan tool will display a low percentage when the EGR valve is commanded closed.

Engine Oil Level Switch: This parameter displays the status of the engine oil level switch as determined by the control module. The control module uses this information to turn on the low engine oil lamp if the engine oil level remains approximately 1 quart low for a sufficient amount of time. The scan tool will display Low when the engine oil level is low. The scan tool will display OK when the engine oil level is correct.

Engine Oil Life Remaining: This parameter displays the amount engine oil life remaining before requiring an oil change based on calculations by the control module. The scan tool will display lower values as the engine oil life approaches 0 miles.

Engine Oil Pressure Sensor: This parameter displays the pressure of the engine oil as calculated by the control module using a signal from the engine oil pressure (EOP) sensor. The scan tool will display oil pressure when the engine is running. The engine oil pressure sensor has a range of values indicating a low value when the oil pressure is low to a high value when the oil pressure is high.

Engine Run Time: This parameter displays the time elapsed since the engine was started. The scan tool will display the time in hours, minutes and seconds. The engine run time will reset to zero when the engine stops running.

Engine Speed: This parameter displays the speed of the crankshaft as determined by the control module using an input from the crankshaft position (CKP) sensor. The scan tool will display a high value at high engine speeds and a low value at low engine speeds.

Fail Counter: This parameter displays the number of times a specific diagnostic has run and failed.

FRP Regulator Command: This parameter displays the fuel rail pressure regulator duty cycle as commanded by the control module. The scan tool will display a lower value for a higher commanded fuel pressure, and a higher value for a lower commanded fuel pressure.

FRP Regulator Command: This parameter displays the current draw of the fuel pressure regulator through the control module. The scan tool will display a higher value for a higher commanded current, and a lower value for a lower commanded current.

FRP Regulator Relay: This parameter displays the commanded state of the relay that supplies power to the fuel pressure regulator through the control module. The scan tool will display ON when the relay is commanded on, and OFF when the relay is commanded OFF. The relay is commanded ON when the ignition is on.

FRP Regulator Fuel Flow Command: This parameter displays the fuel flow through the fuel pressure regulator as calculated by the control module based on engine speed, engine load, fuel pressure regulator current, and fuel pressure sensor inputs. The scan tool will display higher values at higher engine speeds and loads, and lower values at idle.

Front Axle Switch: This parameter displays state of the switch used to determine when the front axle is engaged for operation in four wheel drive. The scan tool will display Locked when the front axle is engaged. The scan tool will display Unlocked when the front axle is disengaged.

Fuel Level Sensor: This parameter displays the voltage received by the control module from the sensor used to monitor the fuel level inside the fuel tank. The scan tool will display a low voltage when the fuel level in the tank is low or near empty. The scan tool will display a high voltage reading when the fuel level in the tank is high or near full.

Fuel Level Sensor: This parameter displays the approximate fuel level in the fuel tank as calculated by the control module based on inputs from the fuel level sensors. The scan tool will display a low value when the fuel level in the tank is low or near empty. The scan tool will display a high value when the fuel level in the tank is high or near full.

Fuel Level Sensor-rear: This parameter displays the voltage received by the control module from the sensor used to monitor the fuel level inside the rear fuel tank. The scan tool will display a low voltage when the fuel level in the tank is low or near empty. The scan tool will display a high voltage reading when the fuel level in the tank is high or near full.

Fuel Temperature Sensor: This parameter displays the current fuel temperature as calculated by the control module based on input from the fuel temperature sensor. The scan tool will display a higher value at higher fuel temperatures. The scan tool will display a lower value at lower fuel temperatures.

GEN L-Terminal Signal: This parameter indicates whether the control module is allowing the generator to operate. The control module can disable the generator under certain conditions. The scan tool will display voltage if the control module is allowing generator operation, while no voltage indicates that the control module is not allowing generator operation.

Glow Plug Relay : This parameter displays the commanded state of the glow plug system. The scan tool will display ON if the glow plugs are being commanded on by the glow plug controller. The scan tool will display OFF if the glow plugs are not being commanded on by the glow plug controller.

High Idle Switch: This parameter displays the state of the high idle request input to the control module from the High Idle Switch. The scan tool will display ON or OFF. ON indicates the control module is receiving a request from the high idle switch to increase engine speed. OFF indicates the control module is not receiving a request from the high idle switch to increase engine speed.

IAT Sensor: This parameter displays the temperature of the air entering the engine as calculated by the control module based on the input from the intake air temperature sensor. The scan tool will display a low value when the air temperature is low, and a high value when the air temperature is high.

Ignition 1 Signal: This parameter displays the voltage measured at the ignition 1 circuit of the control module. Voltage is applied to the control module when the ignition switch is in the ignition 1 position. The scan tool will display a low value when the voltage is low. The scan tool will display a high value, such as battery voltage, when the voltage is higher.

Ignition Off Time: This parameter displays the time elapsed since the ignition was last turned OFF. The scan tool will display the time in hours, minutes and seconds. The ignition off time will reset to zero when the ignition is turned ON.

Injector 1-8 Command: This parameter displays the commanded on time of each fuel injector by the control module. The scan tool will display a low value at idle, and a high value during high engine speeds and loads.

Low Coolant Level: This parameter displays the current status of the low coolant level switch. The scan tool will indicate Yes if the coolant level is low. The scan tool will display No if the coolant level is full.

MAF Sensor (volts): This parameter indicates the voltage signal received from the mass air flow (MAF) sensor by the control module. The scan tool will display a high value at high engine speeds, and a low value at low engine speeds.

Main Injection Command: This parameter displays the commanded on time of the fuel injectors for the main injection pulse. The scan tool will display a higher value for a longer injection pulse. The scan tool will display a lower value for a shorter injection pulse.

Main Injection Fuel Rate: This parameter displays the amount of fuel in the main injection pulse as calculated by the control module. The scan tool will display a higher value for a higher calculated fuel rate. the scan tool will display a lower value for a lower calculated fuel rate.

Main Injection Timing: Indicates the current timing of the main injection pulse as calculated by the control module. The scan tool will display a higher value for a main injection event farther from top dead center (TDC). The scan tool will display a lower value for a main injection event closer to TDC.

MIL Command: This parameter displays the commanded state of the malfunction indicator lamp (MIL) control circuit. The malfunction indicator lamp should be on when the scan tool indicates the MIL Command is On. The malfunction indicator lamp should be off when the scan tool indicates the MIL Command is Off. The control module will command the MIL On when the ignition is ON with the engine OFF in order to perform a bulb check.

Mileage Since First Failure: This parameter displays the mileage accumulated since an emission diagnostic trouble code first failed. The scan tool will display increasing mileage as the vehicle is driven.

Mileage Since Last Failure: This parameter displays the mileage accumulated since an emission diagnostic trouble code last failed. The scan tool will display increasing mileage as the vehicle is driven.

Not Run Counter: This parameter displays the number of ignition cycles that a DTC has not run. The scan tool display will increment as the number of ignition cycles increase without a DTC pass or Fail.

Pass Counter: This parameter displays the number of times a DTC has run and passed. The scan tool display will increment as the number of ignition cycles increase and the DTC passes each ignition cycle.

PCM / VCM in VTD Fail Enable: This parameter indicates the status of the control module communication with the body control module (BCM) The scan tool will display YES if the BCM and the control module lose 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 control module.

PCM Reset: This parameter indicates when the internal control module resets. The scan tool displays YES when an internal PCM reset has occurred. The scan tool displays NO under the normal operating conditions.

Pilot Injection Command: This parameter displays the commanded on time of the fuel injectors for the pilot injection pulse. The scan tool will display a higher value for a longer injection pulse. The scan tool will display a lower value for a shorter injection pulse.

Pilot Injection Fuel Rate: This parameter displays the amount of fuel in the pilot injection pulse as calculated by the control module. The scan tool will display a higher value for a higher calculated fuel rate. the scan tool will display a lower value for a lower calculated fuel rate.

Pilot Injection Timing: Indicates the current timing of the pilot injection pulse as calculated by the control module. The scan tool will display a higher value for a pilot injection event farther from top dead center (TDC). The scan tool will display a lower value for a pilot injection event closer to TDC.

PNP Switch: This parameter indicates the range selection of the automatic transmission as calculated by the control module based on input from the PNP switch. The scan tool will display, In Gear, Park, or Neutral depending on the PNP switch position.

PTO Enable: This parameter indicates all parameter have been met to enable the PTO, and the control module has determined that the PTO is engaged.

PTO Engage Relay Command: This parameter displays the commanded state of the PTO relay control circuit. The scan tool will display ON or OFF. ON indicates the PTO relay control circuit is being grounded by the control module, allowing voltage to the load engage switch. OFF indicates the PTO relay is not being commanded on by the control module.

PTO Engine Shutdown Signal: This parameter displays the input status of the PTO engine shutdown switch to the control module. The scan tool will display YES or NO. Yes indicates the PTO engine shutdown switch is closed, grounding the engine shutoff signal circuit to the control module. OFF indicates the engine shutoff switch is open, allowing normal engine and PTO operation.

PTO Feedback Signal: This parameter displays the state of the power take-off (PTO) based on the signal from the switched side of the PTO relay. The scan tool will display Relay On or Relay Off. Relay On indicates the PTO relay has closed, allowing voltage to the load engage switch. Relay Off indicates the PTO relay is open and the PTO will not engage.

Reverse Enable: This parameter displays the gear selection of the manual transmission as calculated by the control module based on input from the Reverse switch. The scan tool will display YES if the reverse switch is closed. The scan tool will display NO if the reverse switch is open.

Start Up ECT: This parameter Indicates the engine coolant temperature at engine start up as calculated by the control module based on the signal from the ECT sensor. the scan tool will display a higher value on a warmer engine, and a lower value on a colder engine.

Start Up IAT: This parameter Indicates the intake air temperature at engine start up as calculated by the control module based on the signal from the IAT sensor. the scan tool will display a higher value during warmer underhood temperatures, and a lower value during colder underhood temperatures.

Stoplamp Pedal Switch: This parameter displays the state of the brake pedal as determined by the stop lamp pedal switch. This switch turns on the stop lamps when the brake pedal is depressed. The scan tool will display Applied when the brake pedal is depressed, and Released when the brake pedal is not depressed.

TC Learned Closed Position: This parameter displays the difference between the last learned closed position of the turbocharger vanes and the current closed learned position. The scan tool will display a higher value for a larger difference. The scan tool will display a lower value for a smaller difference.

TC Learned Open Position: This parameter displays the difference between the last learned open position of the turbocharger vanes and the current open learned position. The scan tool will display a higher value for a larger difference. The scan tool will display a lower value for a smaller difference.

TC Vane Pos. Ctrl. Solenoid: This parameter displays the current draw of the vane position control solenoid through the control module. The scan tool will display a high current draw when the turbocharger vanes are being commanded closed. The scan tool will display a lower current draw when the turbocharger vanes are being commanded open.

TC Vane Position Learned: This parameter indicates the status of the control module in learning the turbocharger vane position. The Scan tool will display Yes if the turbocharger vane position has been learned. The scan tool will display No if the turbocharger vane position has not been learned. The control module will attempt to relearn during every ignition cycle. A relearn must be completed after any service on the turbocharger or control module.

TC Vane Position Sensor: This parameter displays the current commanded state of the turbocharger vane position control solenoid valve by the control module. The scan tool will display a higher value as the solenoid is commanded open. The scan tool will display a lower value as the solenoid is commanded closed.

TCC/Cruise Brake Pedal Switch: This parameter displays the state of the brake pedal as determined by the control module. The control module monitors the pedal switch on the brake pedal for vehicles equipped with an automatic transmission. The control module uses this information to release the torque convertor clutch when the brake pedal is applied. The scan tool will display Applied when the brake pedal is depressed. the scan tool will display Released when the brake pedal is not applied.

Vehicle Speed Sensor: This parameter indicates the vehicle speed as calculated by the control module based on a signal from the vehicle speed sensor (VSS). the scan tool will display a higher value at higher vehicle speeds, and a lower value at lower vehicle speeds.

VTD Auto Learn Timer: This parameter indicates the status of the theft deterrent system password learn. The scan tool will display ACTIVE if the system is ready to learn a new password. The scan tool will display INACTIVE if the theft deterrent system is not ready to learn a new password.

VTD Fuel Disable: This parameter Indicates if the theft deterrent system is disabling fuel delivery. The scan tool will display ACTIVE if the fuel delivery is being disabled by the theft deterrent system. The scan tool will display INACTIVE if the theft deterrent system is not disabling fuel delivery.

VTD Fuel Disable Until Ign. Off : This parameter Indicates if the theft deterrent system is disabling fuel delivery until the next ignition cycle. The scan tool will display YES if the fuel delivery is being disabled by the theft deterrent system. The scan tool will display NO if the theft deterrent system is not disabling fuel delivery.

Wait to Start: This parameter displays the commanded state of the Wait to Start lamp by the control module. The scan tool will display ON if the lamp is commanded ON. The scan tool will display OFF if the lamp is not commanded ON. Indicates the commanded state of the Wait to Start lamp.

Water in Fuel: This parameter displays the commanded state of the water in fuel lamp by the control module. The scan tool will display ON if the lamp is commanded ON. The scan tool will display OFF if the lamp is not commanded ON. This information is sent by class 2 communication to the IP from the control module.