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.

5 Volt Reference 1-3 Circuit Status: This parameter displays the output voltage of the 5-volt reference circuits from the control module.

A/C Disengage Reason: The parameter displays the A/C compressor disengage reason. There are about 8 possible causes for the A/C compressor to disengage.

A/C Refrigerant Pressure: This parameter displays the pressure from the A/C high side pressure sensor signal circuit to the control module.

A/C Refrigerant Pressure: This parameter displays the voltage from the A/C high side pressure sensor signal circuit to the control module.

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 High Side 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.

Alternator 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.

Ambient Air Temperature Calculated: This parameter displays the calculated ambient air temperature.

APP at Idle: This parameter displays Yes if an angle of the accelerator pedal at idle is calculated by the control module using the signals from the accelerator pedal position sensors. This parameter displays No if no angle of the accelerator pedal at idle is calculated by the control module using the signals from the accelerator pedal position sensors.

APP Sensor 1 or APP Sensor 2: This parameter displays the voltage of the APP sensors signal circuits as measured by the control module.

APP Sensor 1 Indicated or APP Sensor 2 Indicated: This parameter displays the angle of the accelerator pedal position (APP) sensors as calculated by the control module using the signal from the APP sensors. The APP sensors has a range of values indicating a low percentage.

APP Sensors: This parameter displays the angle of the accelerator pedal position (APP) as calculated by the control module using the signals from the APP sensors.

Auto Learn Counter: This parameter indicates the status of the theft deterrent system password learn.

Aux Heater Relay 1 Command: This parameter displays the commanded state of the aux heater relay 1 control circuit. The scan tool will display ON or OFF.

Aux Heater Relay 2 and 3 Command: This parameter displays the commanded state of the aux heater relay 2 and 3 control circuit. The scan tool will display ON or OFF.

Aux Heater Request: This parameter displays the requested state of the aux heater. The scan tool will display ON or OFF.

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.

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

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.

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

Calculated Mass Air Flow: This parameter displays the calculated air flow into the engine. The calculation is used in several diagnostics to determine when to run the diagnostics.

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 Disengage 1-6 History: This parameter displays the history of the action taking with the cruise system.

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 Release Brake Pedal: 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.

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.

Cylinder Air: This parameter displays the actual amount of cylinder air.

Desired Boost: This parameter indicates the desired 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.

Desired Cylinder Air: This parameter displays the difference between the actual amount of cylinder air and the desired amount of cylinder air.

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.

Distance Since DPF Ind ON w/o Regen: This parameter displays the miles since the diesel particulate filter indicator was illuminated without a regeneration occurrence.

Distance Since Last DPF Regeneration: This parameter displays the miles since the last diesel particulate filter regeneration has occurred.

DPF Flow Calculated: The parameter will display the calculated flow of DPF. This parameter is displayed in liters per hour.

DPF Indicator Command: This parameter displays the commanded state of the dpf indicator lamp control circuit. The dpf indicator lamp should be on when the scan tool indicates the DPF Command is On. The dpf indicator lamp should be off when the scan tool indicates the DPF Command is Off.

DPF Regen Command: The parameter will display the DPF regeneration command. This parameter will display in counts.

DPF Regen Interrupted: The parameter will display if the DPF regeneration was interrupted. This parameter will display yes or no.

DPF Regen Inhibit: The parameter will display if the DPF regeneration was inhibited. This parameter will display yes or no.

DPF Soot Mass: This parameter displays the amount of calculated soot in exhaust particulate filter. This parameter will be displayed in grams.

ECM Authentication Status: This parameter displays the status of the control module this ignition cycle. The scan tool will display valid when an internal control module reset has occurred this ignition cycle. The scan tool will display invalid when no internal control module reset has occurred this ignition cycle.

ECM Challenge Status: This parameter displays the status of the control module this ignition cycle. The scan tool will display valid when an internal control module reset has occurred this ignition cycle. The scan tool will display invalid 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.

ECT Sensor: This parameter displays the voltage 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 high voltage. When the coolant temperature is high, the scan tool will display a low voltage.

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 -- 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.

EGR Solenoid Command: This parameter displays ON/OFF. The scan tool will display ON when the EGR valve is commanded open. The scan tool will display OFF when the EGR valve is commanded closed.

EGT Sensor 1 or EGT Sensor 2: This parameter displays the temperature of the exhaust gas calculated by the control module, based on the input from the exhaust gas temperature sensors. When the exhaust gas temperature is low, the scan tool will display a low temperature. When the exhaust gas temperature is high, the scan tool will display a high temperature.

EGT Sensor 1 or EGT Sensor 2: This parameter displays the voltage calculated by the control module, based on the input from the exhaust gas temperature sensors. When the exhaust gas temperature is low, the scan tool will display a high voltage. When the exhaust gas temperature is high, the scan tool will display a low voltage.

Engine Load: This parameter displays the calculated engine load in percent based on inputs to the control module from various engine sensors.

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 Pressure Switch: 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 scan tool will display Low when the engine oil pressure is low. The scan tool will display OK when the engine oil pressure is correct.

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.

Fan Control 1-3 Command: This parameter displays the control module commanded state of the cooling fans.

Fuel Heater Command:: This parameter displays the control modules commanded state of the fuel heater control circuit.

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

Fuel Pressure Regulator 1: This parameter displays the control modules commanded state of the fuel rail pressure regulator 1. This parameter is displayed in milliamperes.

Fuel Pressure Regulator 2: This parameter displays the control modules commanded state of the fuel rail pressure regulator 2. This parameter is displayed in milliamperes.

Fuel Pressure Regulator 2 Command: This parameter displays the fuel rail pressure regulator duty cycle as commanded by the control module.

Fuel Pump Relay: This parameter displays the control modules commanded state of the fuel pump relay control circuit.

Fuel Rail Pressure Sensor: This parameter displays the fuel rail pressure as calculated by the control module using the signal from the fuel rail pressure (FRP) sensor.

Fuel Rail Pressure Sensor: This parameter displays the fuel rail pressure in voltage as calculated by the control module using the signal from the fuel rail pressure (FRP) sensor.

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.

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

GEN F-Terminal Signal: This parameter displays the commanded state of the generator by the control module. A High percentage indicates a high charging command, and a low percentage indicates a low charging command.

Glow Plug: This parameter displays the percentage of 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 Command: This parameter displays the control module commanded state of the glow plug.

Glow Plug Lamp Command: This parameter displays the commanded state of the glow plug lamp circuit by the control module.

IAF Flow Valve Motor Command: This parameter displays the commanded state of the intake air flow valve. This value will be displayed in percent.

IAT Sensor 1 or IAT Sensor 2: 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 sensors. 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: 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.

Immobilizer Programmed: This parameter indicates the status of the immobilizer system. The scan tool will display YES if the immobilizer system is ready to be programmed. The scan tool will display NO if the immobilizer system is not ready to be programmed.

Immobilizer State: This parameter indicates the status of the immobilizer system. The normal parameter display for the immobilizer system is released. If a condition exists with the immobilizer system the parameter will display applied and the vehicle will not start.

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.

Main Injection Fuel Ratio: This parameter displays the air to fuel ratio based on the oxygen sensor inputs. The ECM uses the fuel trims to adjust fueling in order to attempt to maintain a certain air fuel ratio.

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.

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.

Particulate Filter Pressure Variance: This parameter displays the percentage calculated by the control module, based on the input from the exhaust gas temperature sensors when the particulate filter is full and needs a particulate filter regeneration.

Particulate Filter Pressure Variance: This parameter displays the voltage calculated by the control module, based on the input from the exhaust gas temperature sensors when the particulate filter is full and needs a particulate filter regeneration.

Pilot Inj. Trim Average: This parameter displays the average commanded on time of the fuel injectors for the pilot injection pulse.

Pilot Inj. Trim Cyl 1-4 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 (If Equipped): This parameter displays whether the transmission range selector is in park/neutral or in gear.

Security Code Programmed: This parameter indicates the status of the security system. The scan tool will display YES if the security system is ready to be programmed. The scan tool will display NO if the security system is not ready to be programmed.

Starter Relay Command: This parameter displays the commanded state of the starter relay. The scan tool will display on or off.

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

Throttle Position: This parameter displays the percent of throttle opening as calculated by the control module using information from the TP sensor.

Vehicle Speed: 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 Password Learn Enabled: This parameter indicates the status of the theft deterrent system password learn. The scan tool will display YES if the system is ready to learn a new password. The scan tool will display NO if the theft deterrent system is not ready to learn a new password.

VTD Security Code Accepted: This parameter indicates the status of the theft deterrent system security code. The scan tool will display YES if the system has accepted the security code. The scan tool will display NO if the theft deterrent system has not accepted the security code.

VTD Security Code Lockout: 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.

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