Probable Causes
The probable root causes are listed in order below:
• Air inlet system or exhaust system
• Valve lash
• Electronic unit injector
• Boost pressure sensor
• Atmospheric pressure sensor
• Electronic system problem
• Personality module
Recommended Actions
Perform the following diagnostic procedures in order:
1. Check the air inlet system for restrictions or leakage. Check the exhaust system for
restrictions or leakage. Refer to Testing and Adjusting, “Air Inlet and Exhaust System – Inspect”.
2. Check the valve lash. Refer to Testing and Adjusting, “Engine Valve Lash – Inspect/Adjust”.
3. Check the electronic unit injector.
a. Ensure that the front valve cover connector and the rear valve cover connector are fully connected and ensure that the valve cover connectors are free of corrosion.
b. Ensure that the J2/P2 ECM connector is fully connected and ensure that the ECM connector is free of corrosion.
c. Connect the electronic service tool. Perform the “Cylinder Cutout Test”. Access the “Cylinder Cutout Test” by selecting the “Diagnostic Tests” under the “Diagnostics” menu. Run the “Cylinder Cutout Test” in order to disable each cylinder. Disabling each cylinder allows the technician to isolate the
misfiring cylinders.
If the misfiring cylinder can be isolated to a specific cylinder, refer to Troubleshooting,
“Injector Solenoid Circuit – Test”.
4. Check the boost pressure sensor and the atmospheric pressure sensor.
a. While the problem is occurring, check for diagnostic codes that are related to the boost pressure sensor and the atmospheric pressure sensor. If there is an active diagnostic code for a pressure sensor, refer to Troubleshooting, “Engine Pressure Sensor Open or Short Circuit – Test”.
5. Check for an electronic system problem.
a. Monitor the fuel position, the Rated Fuel Limit and the FRC Fuel Limit.
While the vehicle is operating under full load, the parameters should meet the following conditions:
• The fuel position is equal to the Rated Fuel Limit.
• The fuel position is less than the FRC Fuel Limit.
If the fuel position is equal to the Rated Fuel Limit and the fuel position is less than the
FRC Fuel Limit, the Electronics are operating correctly. Go to Step 7.
6. If the fuel position is not equal to the Rated Fuel Limit and/or the fuel position is not less than the
FRC Fuel Limit, perform the following tests in order:
a. When the engine is OFF, turn the key switch to the ON position. Check the boost pressure
on the status screen.
When the engine is OFF, the boost pressure should be 0 kPa (0 psi).
b. Monitor the status for “Accelerator Pedal Position Sensor”. Fully depress the accelerator
pedal and release the accelerator pedal. The status should be 0% at low idle and 100% at high idle.
If the status does not reach 0% or 100%, check the duty cycle of the accelerator pedal position sensor. Select “Monitor Throttle Position Sensor” from the “Calibrations” under the “Service” menu on the electronic service tool in order to monitor the duty cycle of the accelerator pedal position sensor. Fully depress the accelerator pedal and release the accelerator pedal. The accelerator pedal position sensor is within calibration when both of the following conditions are met:
• 10 to 22 percent at low idle
• 75 to 90 percent at high idle
Also, ensure that the duty cycle changes as the pedal position changes.
If a problem with the accelerator pedal position sensor is suspected, refer to Troubleshooting, “Accelerator Pedal (Throttle) Position Sensor Circuit – Test”.
7. Monitor the vehicle speed signal. Ensure the accuracy of the vehicle speed signal by
comparing the vehicle speed signal to the actual vehicle speed.
If the vehicle speed is greater than the VSL, the Power is limited. If a problem is discovered, refer
to Troubleshooting, “Vehicle Speed Circuit – Test”.
8. Check the “Powertrain Data Link”. Ensure that the SAE J1939 Powertrain Data Link is not limiting the power.
a. Monitor the “Powertrain Data Link” status screen while the vehicle is experiencing problems.
If the “Powertrain Data Link” status screen indicates that the “Powertrain Data Link” is limiting the power or the rpm, verify that this is not normal operation. If this is not normal operation, refer to the vehicle OEM for repairs.
9. Check the ECM or the personality module.
a. Verify that the correct personality module has been installed.
Refer to Troubleshooting, “ECM Memory – Test”.
