The Engine Control Module Scan Tool Data Definitions contains a brief description of all engine control module (ECM) related parameters available on the scan tool. The list is arranged in alphabetical order. A given parameter may appear in any one of the data lists. 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.

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 4WD 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 4WD and the front axle indicator switch is open.

A/C Relay Command: This parameter displays the commanded state of the 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 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 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 accelerator pedal position (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 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 1: This parameter displays the angle of the accelerator pedal position (APP) sensor 1 as calculated by the control module using the signal from the APP sensor 1. APP sensor 1 is a range of values indicating a low percentage.

APP Sensor 2: This parameter displays the voltage signal sent to the control module from 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 2: This parameter displays the angle of the accelerator pedal position (APP) sensor 2 as calculated by the control module using the signal from the APP sensor 2. APP sensor 2 is a range of values indicating a low percentage.

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. The scan tool will display a high value at higher barometric pressures, such as sea level. The scan tool will display a lower value at lower barometric pressures, such as higher altitude locations.

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

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.

CKP Sensor Signal Present: This parameter displays an incrementing counter when the control module receives a signal from the crankshaft position (CKP) sensor. The scan tool will display an incrementing counter when the CKP signal is being received by the control module. The scan tool will display a steady number when the CKP signal is not being received by the control module.

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.

Coolant Level Switch: This parameter displays the level of engine coolant as determined by the control module. The control module determines the level of the coolant using the signal from a switch used to monitor the engine coolant level. The scan tool will display low when the engine coolant level is low. The scan tool will display OK when the coolant level is correct.

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.

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 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.

ECM Reset: This parameter displays the status of the control module this ignition cycle. The scan tool will display Yes when an internal control module reset has occurred this ignition cycle. The scan tool will display NO when no internal control module reset has occurred this ignition cycle.

ECT Sensor: This parameter displays the temperature of the engine coolant calculated by the control module, 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 Position Sensor: This parameter displays the voltage signal received from the 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 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 CKP sensor. The scan tool will display a high value at high engine speeds and a low value at low engine speeds.

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.

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.

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: This parameter displays the voltage supply to the glow plugs as measured by the control module. The scan tool will display a higher value at high voltages, or a lower value at lower voltages.

Glow Plug 1-8: This parameter indicates the resistance of the individual glow plug circuits as calculated by the control module. The scan tool will display a higher value for more resistance, and a lower value for less resistance.

Glow Plug Driver Open: This parameter displays the diagnostic state of the output driver for the glow plug circuits. The scan tool will display OK if the circuit is operating correctly. The scan tool will display Fault if there is an open on the circuit.

Glow Plug Driver Shorted: This parameter displays the diagnostic state of the output driver for the glow plug circuits. The scan tool will display OK if the circuit is operating correctly. The scan tool will display Fault if there is an short on the circuit.

Glow Plug Overtemp: This parameter displays the diagnostic state of the output driver for the intake air heater (IAH). The scan tool will display OK if the circuit is operating correctly. The scan tool will display Fault if the circuit is shorted to ground.

Glow Plug Overvoltage: This parameter displays the diagnostic state of the output driver for the glow plug circuits. The scan tool will display OK if the circuits are operating correctly. The scan tool will display Fault if the control module detects that the glow plug voltage is too high.

Glow Plug Undervoltage: This parameter displays the diagnostic state of the output driver for the glow plug circuits. The scan tool will display OK if the circuits are operating correctly. The scan tool will display Fault if the control module detects that the glow plug voltage is too low.

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.

IA Heater Driver Current: This parameter displays the diagnostic state of the current circuit of the IAH. The scan tool will display OK if the circuit is operating correctly. The scan tool will display Fault if the control module detects an incorrect current condition.

IA Heater Driver Grounded: This parameter displays the diagnostic state of the output driver for the IAH. The scan tool will display OK if the circuit is operating correctly. The scan tool will display Fault if the circuit is shorted to ground.

IA Heater Driver Open: This parameter displays the diagnostic state of the output driver for the IAH. The scan tool will display OK if the circuit is operating correctly. The scan tool will display Fault if there is an open on the circuit.

IA Heater Driver Shorted: This parameter displays the diagnostic state of the output driver for the IAH. The scan tool will display OK if the circuit is operating correctly. The scan tool will display Fault if the circuit is shorted to voltage.

IA Heater Overtemp: This parameter displays the diagnostic state of the IAH. The scan tool will display OK if the system is operating correctly. The scan tool will display Fault if the IAH is overheating.

IA Heater Overvoltage: This parameter displays the diagnostic state of the IAH. The scan tool will display OK if the system is operating correctly. The scan tool will display Fault if the control module detects that the IAH voltage is too high.

IA Heater Undervoltage: This parameter displays the diagnostic state of the IAH. The scan tool will display OK if the system is operating correctly. The scan tool will display Fault if the control module detects that the IAH voltage is too low.

IAT Sensor 1: This parameter displays the temperature of the air entering the engine air duct as calculated by the control module based on the input from the intake air temperature 1 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.

IAT Sensor 2: This parameter displays the temperature of the air entering the engine intake manifold as calculated by the control module based on the input from the intake air temperature 2 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.

Intake Air Heater: This parameter displays the current voltage of the IAH as calculated by the control module based on input from the IAH on the voltage signal circuit. The scan tool will display a higher value at higher voltages. The scan tool will display a lower value at lower voltages.

Intake Air Heater: This parameter displays the on-time or duty cycle of the IAH as reported to the control module from the IAH module on the IAH feedback signal circuit.

Intake Air Heater Command: This parameter displays the on-time or duty cycle of the IAH as commanded by the control module.

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

MAF Sensor (volts): This parameter indicates the voltage signal received from the 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 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.

MAP Sensor: This parameter indicates the manifold absolute pressure inside the engine as calculated by the control module based on the signal from the manifold absolute pressure (MAP) sensor. The scan tool will display a higher value wide open throttle, and a lower value at idle.

MAP Sensor: This parameter indicates the voltage signal received by the control module from the MAP sensor. The scan tool displays a low voltage at idle, and a high voltage at wide open throttle. Barometric pressure and altitude can effect these values.

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.

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.

PNP Switch: This parameter indicates the range selection of the automatic transmission as calculated by the control module based on input from the park/neutral position (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 power take off (PTO), and the control module has determined that the power take off (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 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 engine coolant temperature (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 intake air temperature (IAT) sensor. the scan tool will display a higher value during warmer underhood temperatures, and a lower value during colder underhood temperatures.

Stop Lamp 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 lamp 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 Position Lrn. This Run Cycle: 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 this ignition cycle. The scan tool will display No if the turbocharger vane position has not been learned this ignition cycle. 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 Lrn. Since DTC Clear: 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 any time after the DTCs have been cleared. The scan tool will display No if the turbocharger vane position has not been learned since the last DTC clear. 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.

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.

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 Sensor: 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 instrument panel (I/P) from the control module.