Scan Tool Data Definitions - Powertrain Systems

Scan Tool Data Definitions

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 ECM from the heating, ventilation, and air conditioning (HVAC) controls.

The scan tool will display Yes or No. Yes indicates the ECM 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 ECM 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 ECM 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 psi or MPa.

Actual Suction Control Valve Control Current:
This parameter displays the suction control valve (SCV) control current as calculated by the ECM. This can be compared the desired suction control valve control current to determine SCV accuracy or supply pump problems.

APP Indicated Angle:
This parameter displays the angle of the accelerator pedal as calculated by the ECM 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 ECM 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 ECM from accelerator pedal position (APP) sensor 2 of the APP sensor assembly. APP sensor 2 is a range of values indicating a high voltage when the accelerator pedal is not depressed to a middle voltage when the accelerator pedal is fully depressed.

APP Sensor 3:
This parameter displays the voltage signal sent to the ECM 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 middle voltage when the accelerator pedal is fully depressed.

Balancing Rate Cyl. 1:
This parameter displays the adjustment in fuel volume for cylinder 1 at low engine speed area (from idle to around 1000 RPM) as calculated by the ECM. 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 at low engine speed area (from idle to around 1000 RPM) as calculated by the ECM. 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 at low engine speed area (from idle to around 1000 RPM) as calculated by the ECM. 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 at low engine speed area (from idle to around 1000 RPM) as calculated by the ECM. 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 ECM using the signal from the barometric pressure (BARO) sensor inside of the ECM.

Basic Fuel Rate:
This parameter displays the basic fuel rate as calculated by the ECM based on the signal from the engine speed and accelerator pedal position. The scan tool will display more fuel rate if the engine load is increased as the accelerator pedal is stepped on at constant engine speed.

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

Boost Pressure Sensor:
This parameter displays 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 Camshaft Position (CMP) Sensor signal to the ECM. The scan tool will display Yes or No. Yes indicates the CMP signal is being received by the ECM. No indicates the CMP signal is not being received by the ECM.

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

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

Cruise Control Active :
This parameter displays the status of the cruise control system as determined by the ECM. 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 Cruise On/Off switch input to the ECM. When the Cruise Main switch is pushed, the scan tool displays ON.

Cruise Release Brake Switch:
This parameter displays the state of the Cruise Release Brake Switch as determined by the ECM. The scan tool will display Released or Applied. Released indicates the brake pedal is not being pushed down, allowing the cruise control to be enabled. Applied indicates the brake switch is being applied, disabling cruise control operation.

Cruise Resume/Accel. Switch:
This parameter displays the state of the Cruise Resume/Accel. switch input to the ECM. When the Resume/Accel. switch is pushed, the scan tool displays ON.

Cruise Set/Coast Switch:
This parameter displays the state of the Cruise Set/ Coast switch input to the ECM. When the Set/Coast switch is pushed, the scan tool displays ON.

Desired EGR Position:
This parameter displays the EGR valve position desired by the ECM based on current sensor inputs. This can be compared to the EGR position sensor to determine sensor accuracy or EGR valve problems.

Desired Fuel Rail Pressure:
This parameter displays 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:
This parameter displays the idle speed 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.

Desired Suction Control Valve Control Current :
This parameter displays the suction control valve (SCV) control current by the ECM based on current sensor inputs. This can be compared the actual rail pressure control valve to determine SCV accuracy or supply pump problems.

DTC Set This Ignition:
This parameter displays Yes 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 a voltage input from the engine coolant temperature (ECT) sensor to the ECM. The scan tool will display a low temperature when signal voltage is high, and a high temperature when the signal voltage is low.

EGR Learned Minimum Position:
This parameter displays the learned position at the EGR valve closed position using the signal from the EGR valve position sensor.

EGR Position Sensor:
This parameter displays the EGR valve position calculated by the ECM using the signal from the EGR position sensor. The EGR valve current position is a range of values indicating a low percentage when the EGR valve is closed to a high percentage when the EGR valve is opened.

EGR Position Variance:
This parameter displays the amount of the EGR valve deviation between the desired EGR valve position and the actual EGR valve position using the signal from the EGR valve position sensor.

EGR Solenoid Command:
This parameter displays the EGR valve control duty ratio calculated by the ECM using the signal from engine speed, engine coolant temperature and injection volume.

Engine Run Time:
This parameter displays the time elapsed since the ignition switch is ON. The scan tool will display the time in hours, minutes and seconds. The engine run time will reset to zero as soon as the ignition switch is OFF.

Engine Speed:
This parameter displays the speed of the crankshaft as calculated by the ECM based on inputs from the crankshaft position (CKP) sensor and camshaft position (CMP) sensor. The scan tool will display the engine speed in revolution per minute (RPM).

Exhaust Brake Relay:
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 ECM, allowing voltage to the exhaust brake solenoid. OFF indicates the exhaust brake relay is not being commanded on by the ECM.

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

Final Fuel Rate:
This parameter displays the final fuel rate as calculated by the ECM. The basic fuel rate calculated from the engine speed and accelerator pedal position is compared with the fuel rate which added the compensation by the various sensor input to the maximum fuel rate calculated from the engine speed. The fewer one is determined as the final fuel rate.

Fuel Temperature Sensor:
This parameter displays the temperature of the fuel based on a voltage input from the fuel temperature (FT) sensor to the ECM. The scan tool will display a low temperature when signal voltage is high, and a high temperature when the signal voltage is low.

Fuel Rate at Start:
This parameter displays the fuel rate at the startup as calculated by the ECM based on the signal from the engine coolant temperature (ECT) sensor and starter switch input signal. The scan tool will display more fuel rate if the engine coolant is cold.

Fuel Rate Correction:
This parameter displays the compensated final fuel rate as calculated by the ECM based on the final fuel rate and engine running condition.

Glow Plug Relay:
This parameter displays the commanded state of the glow plug relay control circuit. The scan tool will display ON or OFF. ON indicates the glow plug relay control circuit is being grounded by the ECM, allowing voltage to the glow plugs. OFF indicates the glow plug relay is not being commanded on by the ECM.

IAT Sensor:
This parameter displays the temperature of the intake air based on a voltage input from the intake air temperature (IAT) sensor to the ECM. The scan tool will display a low temperature when signal voltage is high, and a high temperature when the signal voltage is low. Note that the IAT sensor is internal to the MAF sensor and the MAF sensor is heated.

Idle Up Volume:
This parameter displays the voltage signal sent to the ECM from the idle up volume switch. The idle up volume is a range of values indicating a low voltage when the idle up volume rotates counterclockwise direction to a high voltage when the idle up volume rotates clockwise direction.

Ignition 1 Signal:
This parameter displays the voltage measured at the ignition feed circuit of the ECM. Voltage is applied to the ECM when the ignition switch is ON position.

Injector 1 Command:
This parameter is the time the ECM turns on the fuel injector for cylinder No. 1. The scan tool will display a higher value with a longer pulse width, or a lower value with a shorter pulse width.

Injector 2 Command:
This parameter is the time the ECM turns on the fuel injector for cylinder No. 2. The scan tool will display a higher value with a longer pulse width, or a lower value with a shorter pulse width.

Injector 3 Command:
This parameter is the time the ECM turns on the fuel injector for cylinder No. 3. The scan tool will display a higher value with a longer pulse width, or a lower value with a shorter pulse width.

Injector 4 Command:
This parameter is the time the ECM turns on the fuel injector for cylinder No. 4. The scan tool will display a higher value with a longer pulse width, or a lower value with a shorter pulse width.

MAF Sensor:
This parameter displays the air flow into the engine as calculated by the ECM based on the mass air flow (MAF) sensor input. The scan tool will displays a high value at higher engine speeds, and a low value at idle.

Main Injection Timing:
This parameter is the injection timing calculated by the ECM based on the CKP sensor and CMP sensor inputs using a target injection timing map. This timing is compensated by engine coolant temperature, altitude, and intake air temperature, etc.

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

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

PTO Accelerator Sensor (If Equipped):
This parameter displays the voltage signal sent to the ECM from the PTO accelerator sensor. The PTO accelerator sensor is a range of values indicating a low voltage when the accelerator volume is not operated to a high voltage when the accelerator volume is fully operated.

PTO Enable (If Equipped):
This parameter displays all parameters have been met to enable the PTO, and the ECM has determined that the PTO is engaged.

PTO Engage Relay Command (If Equipped):
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 ECM, allowing voltage to the load engage switch. OFF indicates the PTO relay is not being commanded on by the ECM.

PTO Engine Shutdown Signal (If Equipped):
This parameter displays the input status of the PTO engine shutdown switch to the ECM. 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 ECM. No indicates the engine shutoff switch is open, allowing normal engine and PTO operation.

PTO Feedback Signal (If Equipped):
This parameter displays a feedback signal based on the signal from the PTO relay feedback switch. 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.

Stoplamp Pedal Switch:
This parameter displays the state of the brake pedal as determined by the ECM based on an input from 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.

Start Up ECT:
This parameter displays the engine coolant temperature at start up, as calculated by the ECM based on the input from the engine coolant temperature sensor. The scan tool will display a higher value at higher start up temperatures.

Vehicle Speed Sensor:
This parameter displays the vehicle speed calculated by the ECM based on an input from the vehicle speed sensor (VSS). The scan tool will display a high value at higher vehicle speeds, and a low value at lower vehicle speeds.