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.

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.

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: This parameter displays the adjustment in fuel volume for cylinder 1 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.

Balancing Rate Cyl. 2: This parameter displays the adjustment in fuel volume for cylinder 2 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.

Balancing Rate Cyl. 3: This parameter displays the adjustment in fuel volume for cylinder 3 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.

Balancing Rate Cyl. 4: This parameter displays the adjustment in fuel volume for cylinder 4 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.

Balancing Rate Cyl. 5: This parameter displays the adjustment in fuel volume for cylinder 5 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.

Balancing Rate Cyl. 6: This parameter displays the adjustment in fuel volume for cylinder 6 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.

Basic Fuel Rate: This indicates the basic PC valve on time as commanded by the ECM.

Battery Voltage: This represents the system voltage measured by the ECM at the ECM battery voltage feed circuit.

Boost Pressure Sensor: The amount of turbo boost pressure in the intake manifold. True boost pressure is determined by subtracting BARO from the actual reading.

CAM Signal Present: This parameter displays the status of the Ignition pump cam position (CAM) signal to the control module. The scan tool will display Yes or No. Yes indicates the CAM signal is being received by the control module. No indicates the CAM signal is not being received by the control module.

Clutch Pedal Switch: This indicates the current state of the clutch pedal switch when vehicle has a manual transmission.

Crank Signal Present: This parameter displays the status of the Crankshaft Position Sensor (CKP) signal to the control module. The scan tool will display Yes or No. Yes indicates the CKP signal is being received by the control module. No indicates the CKP signal is not being received by the control module.

Cruise Control Active: Indicates the current state of the cruise control system.

Cruise ON/OFF Switch: Indicates the current state of the cruise ON/OFF switch.

Cruise Resume/Accel Switch: Indicates the current state of the cruise Resume/Accel switch.

Cruise Set Coast Switch-Range ON/OFF: Indicates the current state of the cruise set coast switch.

Desired Fuel Rail Pressure: Indicates the fuel rail pressure desired by the ECM based on current sensor inputs. This can be compared the actual fuel rail pressure to determine sensor accuracy or fuel pressure problems.

Desired Idle Speed: The idle speed that is requested by the ECM. The ECM will compensate for various engine loads based on engine coolant temperature (ECT) to keep the engine at the desired speed.

DTC Set This Ignition: Indicates if a diagnostic trouble code (DTC) has set this ignition cycle.

ECT Sensor: The ECT sensor sends a signal to the ECM 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 ECM monitors a high signal voltage and interprets the high signal voltage as a cold engine. As the sensor warms, internal resistance decreases, the voltage signal will decrease and the ECM will interpret the lower voltage as a warm engine.

Engine Oil Level Switch: Indicates the current status of the engine oil level switch.

Engine Oil Life Remaining: Indicates the calculated current oil life remaining according to the ECM. This is based on ECM calculations of mileage, driving conditions, temperature, and load conditions.

Engine Run Time: 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: Engine speed is computed by the ECM from the CKP sensor. If the CKP sensor is inoperative, an RPM reading is taken from the injection pump cam signal. The reading should remain close to desired idle under various engine loads with the engine idling. Engine speed value is very accurate.

Exhaust Brake Relay Command: This parameter displays the commanded state of the exhaust brake relay control circuit. The scan tool will display ON or OFF. ON indicates the exhaust brake relay control circuit is being grounded by the control module, allowing voltage to the exhaust brake solenoid. OFF indicates the exhaust brake relay is not being commanded on by the control module.

Exhaust Brake Switch: This parameter displays the input status of the exhaust brake switch to the control module. The scan tool will display ON or OFF. ON indicates the exhaust brake switch is closing the exhaust brake request circuit to the control module. OFF indicates the exhaust brake switch is open.

Final Fuel Rate: This parameter indicates the actual fuel rate as calculated by the ECM. The ECM attempts to adjust this rate to bring it close to the Basic Fuel Rate.

Fuel Level Sensor: Indicates the current fuel level percentage in the fuel tanks.

Fuel Rate Correction: This parameter displays the average adjustment and fuel volume for each cylinder as calculated by the control module. The scan tool will display a negative value if the fuel volume is lowered. The scan tool will display a positive value if the fuel volume is increased.

Fuel Rate at Start: Indicates the startup fuel rate.

Fuel Temperature Sensor: There is a thermistor located in the optical sensor that determines fuel temperature. When the sensor is cold, internal resistance high, the ECM 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 ECM will interpret the low voltage as warm fuel.

GEN L Terminal Signal: Indicates the commanded state of the GEN L terminal.

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

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: The intake air temperature (IAT) sensor sends a signal to the PCM relative to the incoming air. The IAT is used by the ECM to adjust fuel delivery.

Ignition 1 Signal: This represents the system voltage measured by the ECM at its ignition feed circuit. Ignition voltage is only present when the ignition is turned ON.

Injector 1-6 Command: Indicates the commanded state of the fuel injectors in milliseconds (ms).

Intake Air Heater Relay Command: Scan tool displays ON/OFF. Indicates the commanded state of the Intake Air Heater relay.

Low Coolant Level: Indicates if the low coolant switch has been activated.

Main Injection Timing: Indicates the current timing of the main injection pulse.

MIL Command: Represents the commanded state of the service engine soon/malfunction indicator lamp (MIL).

PCM Reset: Indicates if the ECM has been reset this ignition.

PNP Switch: Indicates the current state of the PNP switch.

Power Relay Status: This parameter displays the commanded state of the power relay control circuit. The scan tool will display ON or OFF. ON indicates the power relay control circuit is being grounded by the control module, allowing voltage to the other circuits of the control module. OFF indicates the power relay is not being commanded on by the control module.

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.

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.

Reverse Enable: Indicates if the vehicle is in reverse.

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

Start Up ECT: A reading of the vehicles coolant temperature at startup. This will change every key cycle.

Stop Lamp Pedal Switch: This indicates the current state of the stop lamp pedal switch.

Two Speed Axle Switch: This parameter displays the state of the two speed axle based on the signal from the two speed axle switch. The scan tool will display high gear or low gear. High gear indicates the axle is in high 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.

Vehicle Speed Sensor: Vehicle speed is a ECM 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 and kilometers per hour (km/h) and miles per hour (mph).

Wait to Start: Indicates the commanded state of the Wait to start lamp