Probable Causes
The probable root causes are listed in order below:
• Diagnostic codes
• Intake valve actuation system
• Cold mode
• Customer specified parameters (normal operation)
• Electronic system problem
• Fuel supply
• Leakage in Air-to-Air Aftercooler Core
• Air inlet system or exhaust system
• Individual malfunctioning cylinder
• Torque limit switch
Recommended Actions
Diagnostic Codes
1. Connect the Caterpillar Electronic Technician (Cat ET) to the data link connector.
2. Check for active codes and/or logged codes.
Troubleshoot any codes that are present before continuing with this procedure.
Note: Certain diagnostic codes may cause poor performance.
Intake Valve Actuation System
1. Start the engine.
2. Monitor the status screens on Cat ET.
3. Check for an “Intake Vlave System Starting” flag at the top left of any status screen.
Note: The engine will not receive full power until the “Intake Vlave System Starting” flag becomes inactive.
Cold Mode
1. Start the engine.
2. Monitor the status screens on Cat ET.
3. Check for a “Cold Mode” flag at the top of any status screen.
Note: The engine will not receive full power until the “Cold Mode” flag becomes inactive.
Customer Specified Parameters
1. Verify that the complaint is not normal operation (programmed parameter).
2. Access the “Configuration” screen on Cat ET.
3. Check the following parameters:
• “Rating Number”
• “Top Engine Limit”
• “Vehicle Speed Limit”
• “Lower Gears Engine RPM Limit”
• “Intermediate Gears Engine RPM Limit”
• “Gear Down Protction Engine RPM Limit”
Note: If the “Rating Number” is programmed to 0, the engine is limited to 119 kW (160 hp).
4. Set each parameter to the parameter’s maximum value one at a time and determine whether the problem is corrected.
Electronic System Problem
1. 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.
2. 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 3.
3. 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:
4. 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).
5. Monitor the status of the accelerator pedal position sensor. Operate the engine at high idle with the vehicle in Neutral.
If the engine can not reach the programmed “Top Engine Limit”, check the duty cycle for the accelerator pedal position sensor in order to ensure that the duty cycle is within calibration (75 to 90 Percent at high idle).
If the accelerator pedal position is unstable, check the duty cycle of the accelerator pedal position sensor. Check the duty cycle by slowly operating the accelerator pedal in order to verify that the accelerator pedal position sensor is within calibration. 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”.
Note: If the engine exceeds the Top Engine Limit, the “Top Engine Limit with Droop” is programmed to YES.
6. 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”.
7. Check the “Power train Data Link”. Ensure that the power train data link is not limiting the power.
a. Monitor the “Power train Data Link” status screen while the vehicle is experiencing problems.
If the “Power train Data Link” status screen indicates that the “Power train 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.
Fuel Supply
1. Monitor the exhaust for smoke while the engine is being cranked.
If no smoke is present, there may be a problem with the fuel quality or there may be a problem with the fuel supply.
2. Check the fuel quality. Refer to Testing and Adjusting, “Fuel Quality – Test”. Also refer to the Truck Performance and Driveability Diagnostic Guide, LEBT3477.
3. Check the fuel pressure. Refer to Testing and Adjusting, “Fuel System Pressure – Test”.
4. Ensure that the fuel system has been primed.
Refer to Testing and Adjusting, “Fuel System – Prime”.
5. Check for fuel supply lines that are restricted.
6. Check the fuel filters.
7. If the temperature is below 0 C (32 F), check for solidified fuel (wax).
8. Check for air in the fuel system. Refer to Testing and Adjusting, “Air in Fuel – Test”.
Air Inlet System or Exhaust System
1. Check for leakage in the Air-to-Air Aftercooler Core . Refer to Testing and Adjusting, “Aftercooler – Test”.
2. Check the air intake system for restrictions or leakage. Check the exhaust system for restrictions or leakage. Refer to Testing and Adjusting, “Air Inlet and Exhaust System – Inspect”.
Individual Malfunctioning Cylinder
1. 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.
2. Ensure that the J2/P2 ECM connector is fully connected and ensure that the ECM connector is free of corrosion.
3. Use the “Cylinder Cutout Test”. Access the “Cylinder Cutout Test” by selecting the “Diagnostics Test” under the “Diagnostic” 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. Perform a PAR Test (Performance Analysis Report).
Torque Limit Switch
1. Check the setting for the customer parameter for the “Torque Limit”.
If the “Torque Limit” is programmed below 3400 N·m (2500 lb ft), check the status screen for the Torque Limit Switch. Ensure that the status screen indicates that the torque limit switch is OFF. If the status of the torque limit switch is ON and a “Torque Limit” is programmed, the system is operating correctly. If the switch that is connected to this signal input is not switching ON and switching OFF, refer to Troubleshooting, “PTO Switch Circuit – Test”.
