3126B and 3126E On-highway Engines Caterpillar

Probable Causes

The probable root causes are listed in order below:

• Customer Specified Parameters

• Electronic system

• Cold Mode operation

• Malfunction of an individual cylinder

• Power Train Data Link

• ECM or Personality Module

• Torque limit switch

• Theft Deterrent

• Injection actuation pressure

• Combustion problem

Recommended Actions

Perform the following diagnostic procedures in order:

Customer Specified Parameters

1. Check Customer Specified Parameters.

2. Verify that the complaint is not normal operation (programmed parameter).

3. Connect Caterpillar Electronic Technician (ET) to the cab data link connector.

4. Check the following parameters:
   • "Rating Number"

   • "Top Engine Limit"

   • "Vehicle Speed Limit"

   • "Lower Gears Engine RPM Limit"

   • "Intermediate Gears Engine RPM Limit"

   • "Gear Down Protection Engine RPM Limit"

5. Set each parameter to the parameter's maximum value one at a time and determine whether the problem is corrected.

Electronic System

1. Connect ET to the cab data link connector.

2. While the problem is occurring, check for diagnostic codes that are related to the boost pressure sensor and the atmospheric pressure sensor. If a diagnostic code is found, refer to Troubleshooting, "Engine Pressure Sensor Open or Short Circuit - Test".

3. Monitor the fuel position, the rated fuel limit and the fuel limit for fuel ratio control (FRC).

   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 limit.

   If the fuel position is equal to the rated fuel limit and the fuel position is less than the FRC limit, the electronics are operating correctly.

4. If the fuel position is not equal to the rated fuel limit and/or the fuel position is not less than the FRC limit, perform the following tests in order:

5. When the engine is OFF, turn the ignition key switch to the ON position. Check the boost pressure on the ET status screen. When the engine is OFF, the boost pressure should be 0 kPa (0 psi).

Cold Mode Operation

Note: This is normal operation if the problem occurs only after start-up in cold weather.

1. Connect ET to the cab data link connector.

2. Use ET to verify that the engine has progressed from cold mode. An active cold mode is indicated in the upper corner of any status screen.

Individual Cylinder Malfunction

1. Ensure that the electronic unit injector connector (J300/P300) is fully connected and ensure that the electronic unit injector connector (J300/P300) is free of corrosion.

2. Ensure that the ECM engine harness connector (J2/P2) is fully connected and ensure that the engine harness connector (J2/P2) is free of corrosion.

3. Connect ET to the cab data link connector. Use the Cylinder Cutout Test. Access the Cylinder Cutout Test by selecting the "Diagnostic Menu" and the "Diagnostics Test 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 Performance Analysis Report (PAR).

Power Train Data Link

1. Check the "Powertrain Data Link". Ensure that the SAE J1939 data link is not limiting the power.

2. Connect ET to the cab data link connector.

3. Monitor the "Powertrain Data Link" status screen while the vehicle is experiencing problems.

   If the "Powertrain Data Link" status screen indicates that the 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.

ECM or Personality Module

Check the ECM or the Personality Module.

Refer to Troubleshooting, "ECM Memory - Test".

Torque Limit Switch

1. Connect ET to the cab data link connector.

2. Check the setting for the Customer Parameter for the "Torque Limit". If the "Torque Limit" is programmed below 2712 N·m (2000 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".

Theft Deterrent

Ensure that the theft deterrent (if equipped) is not active. Turn the ignition switch to the ON position. Observe the display screen on the CAT ID. If the display screen on the CAT ID indicates that the theft deterrent is enabled, the Theft Deterrent Passwords must be entered before the engine will start.

Injection Actuation Pressure System

Note: Check the actual injection actuation pressure against the desired injection actuation pressure.

1. Crank the engine and monitor the Injection actuation pressure and the injection actuation pressure control valve. The high pressure oil system is operating properly if the pressure output is a minimum of 6 MPa (870 psi).

2. Connect ET and check for event code 164-11 injection actuation pressure system fault. If an 164-11 event code has been logged recently, refer to Troubleshooting, "Injection Actuation Pressure System - Test".

3. If higher than actual pressure is being indicated, then disconnect the injection actuation pressure sensor and try to start the engine. If the engine starts, refer to Troubleshooting, "Injection Actuation Pressure Sensor - Test".

Combustion Problem

Check for combustion problems.

Examples of combustion problems are shown in the following list:

• Outside temperatures are too cold.

• Mechanical problem