C13, C15, and C18 Engines Troubleshooting – Power Is Intermittently Low or Power Cutout Is Intermittent

Note: Use this procedure only if the engine does not shut down completely.

Note: Refer to Troubleshooting, “Cat ET Service Features” for information about service features.

Probable Causes


  • Check for diagnostic trouble codes 
  • Electrical connections not properly connected. 
  • Intermittent throttle signal 
  • Fuel system components 
  • Fuel supply pressure 
  • Restriction in the air inlet and exhaust system 
  • Excessive temperature of the turbocharger that causes engine derate 

Recommended Actions

Note: If the problem only occurs under certain conditions, test the engine under those conditions. Examples of certain conditions are high engine speed, full load, and engine operating temperature. Troubleshooting the symptoms under other conditions can give misleading results.

Table 1
Troubleshooting Test Steps Values Results
1. Diagnostic Codes

A. Certain codes may derate engine power. Connect Caterpillar Electronic Technician (ET) and check for active codes and/or for logged codes.

Diagnostic codes Result: A diagnostic code is active or logged.

Troubleshoot any codes that are present before continuing with this procedure.

Result: A diagnostic code is not active or logged.

Proceed to Test Step 2.

2. Electrical Connections

A. Verify that the following connectors are installed correctly:

1. Electrical connectors for the ECM
2. Connectors for the wiring harness under the valve cover
3. Connectors for the engine speed/timing sensors

Electrical connectors Result: The connectors are installed correctly.

Proceed to Test Step 3.

Result: The connectors are not installed correctly.

Install the connectors correctly. Refer toTroubleshooting, “Electrical Connectors – Inspect” for the proper troubleshooting procedure.

3. Check for Intermittent Diagnostic Codes

A. Certain diagnostic codes may cause poor performance. Connect Cat ET and check for active codes and/or for logged codes.

Intermittent codes Result: Intermittent codes are present.

Troubleshoot any codes that are present before continuing with this procedure.

Result: Intermittent codes are not present.

Proceed to Test Step 4.

4. Intermittent Throttle Signal

A. Monitor the status for “Throttle Position” on Cat ET.

B. Verify that the status for “Throttle Position” is stable and that the engine is able to reach high idle speed.

Refer to Troubleshooting, “Speed Control – Test”.

Throttle signal Result: The status for “Throttle Position” is stable.

Proceed to Test Step 5.

Result: The status for “Throttle Position” is not stable.

Make the necessary repairs. Refer to Troubleshooting, “Speed Control – Test”.

5. Fuel System

A. Ensure that the fuel system is operating properly.

B. Start the engine.

C. Perform the “Fuel System Verification Test” on Cat ET.

Fuel System Verification Test Result: The “Fuel System Verification Test” was successful.

Proceed to Test Step 6.

Result: The “Fuel System Verification Test” was not successful.

Repair the cylinders that failed the “Fuel System Verification Test”. Reset all active codes and clear all logged codes. Verify that the repair has eliminated the problem in the cylinder.

6. Fuel Supply Pressure

A. Check the fuel pressure. Ensure that the fuel is stable. Refer to Systems Operation/Testing and Adjusting for the procedure to check the fuel pressure manually.

B. Visually check the fuel level. Do not rely on the fuel gauge only. If necessary, add fuel. If the engine has been run out of fuel, purge the air from the fuel system.

C. Ensure that the fuel supply valve (if equipped) is in the full OPEN position.

D. Check the fuel lines for the following problems:

1. Restrictions
2. Collapsed lines
3. Pinched lines
4. Loose connections

E. Prime the fuel system if any of the following procedures have been performed:

1. Replacement of the fuel filters
2. Service on the low-pressure fuel supply circuit
3. Replacement of unit injectors

F. Check the fuel tank for foreign objects which may block the fuel supply.

G. Check the fuel filters.

H. Check the fuel quality. Make sure that the fuel meets the requirements of Special Publication, SEBU6250, “Caterpillar Machine Fluids Recommendations “.

Cold weather adversely affects the characteristics of the fuel. Refer to the Operation and Maintenance Manual for information on improving the characteristics of the fuel during cold-weather operation.

Fuel supply Result: The fuel supply is stable.

Proceed to Test Step 7.

Result: The fuel supply is not stable.

Make the necessary repairs.

Verify that the repair eliminates the problem.

7. Restriction in the Air Inlet and Exhaust System

Inlet air restrictions or exhaust system restrictions can cause a high exhaust temperature.

The Engine Control Module (ECM) monitors the following parameters in order to calculate an exhaust temperature:
1. Barometric pressure
2. Intake manifold air temperature
3. Engine speed

Certain operating conditions may cause the calculated exhaust temperature to increase to a level that may damage engine components. If a high exhaust temperature occurs, the ECM derates the engine in order to reduce the calculated exhaust temperature. The engine is derated only to a level that allows the calculated exhaust temperature to return to an acceptable level.

Refer to the High Exhaust Temperature Prevention Derate Time Histogram for derate information.

A. Ensure that the turbocharger is operating correctly. Periodic inspection and cleaning are recommended for the turbocharger compressor housing (inlet side).

B. Check the air filter restriction indicator. Clean plugged air filters or replace plugged air filters.

C. Check the air inlet and exhaust system for restrictions and/or leaks.

Restrictions Result: There are restrictions in the air inlet or exhaust system.

Repair the restrictions or remove the restrictions.

Complete the procedure in the order in which the steps are listed.

If the procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).

Posted in C18

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