SUPPORT AS 9Y2029 - Caterpillar

Probable Causes
Diagnostic codes
Electrical connectors
Fuel supply
Cold mode operation and cold cylinder cutout
Throttle signal
Unit injectors
Air inlet and exhaust systemRecommended Actions
Note: If the symptom only occurs under certain operating conditions (high idle, full load, engine operating temperature, etc), test the engine under those conditions. Troubleshooting the symptom under other conditions can give misleading results.
Table 1
Troubleshooting Test Steps Values Results
1. Check for Diagnostic Codes
A. Check for codes on Cat® Electronic Technician (ET).
Diagnostic Codes
Results: There are no diagnostic codes.
Proceed to Test Step 2.
Results: There are active or logged diagnostic codes.
Repair: Troubleshoot the diagnostic codes before continuing with this procedure.
2. Inspect the Electrical Connectors
A. Check for correct installation of the J1/P1 and J2/P2 Electronic Control Module (ECM) connectors and the unit injector connectors. Refer to Troubleshooting, "Inspecting Electrical Connectors".
Electrical Connectors
Result: The electrical connectors are OK.
Proceed to Test Step 3.
Result: Repair or replace any worn or damaged electrical connectors.
3. Check the Fuel Supply
A. Check the fuel level in the fuel tank. Ensure that adequate fuel is available for the application.
B. Check fuel lines for the following problems: restrictions, collapse and pinched line.
C. Check the fuel tank for foreign objects which may block the fuel supply. Check for air leaks in the suction line of the fuel pump.
Note: 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.
D. Check the fuel pressure during engine operation. Check the fuel pressure after the fuel filter. Refer to the Systems Operation/Testing and Adjusting manual for the correct pressure values. If the fuel pressure is low, replace the fuel filters. If the fuel pressure is still low, check the following items: fuel transfer pump, fuel transfer pump coupling and fuel pressure regulating valve.
Fuel Supply
Result: The fuel supply is OK.
Proceed to Test Step 4.
Result: The fuel supply is NOT OK.
Repair: Repair or replace any worn or damaged components pertaining to the fuel supply.
4. Check for Cold Mode Operation and Cold Cylinder Cutout
A. Use Cat ET in order to verify that the engine has exited cold mode. During cold mode, fuel injection timing is modified. When the engine is in cold mode, the cold cylinder cutout strategy may be active. Cold mode cylinder cutouts may cause variations in vibration and available power. This is normal operation.
Cold Mode Operation and Cold Cylinder Cutout
Result: Cold Mode Operation and Cold Cylinder Cutout are OK.
Proceed to Test Step 5.
Result: Cold Mode Operation and Cold Cylinder Cutout are NOT OK.
Repair: Troubleshoot the reason the engine is in Cold Mode Operation or Cold Cylinder Cutout.
5. Check the Throttle Signal
A. Monitor the throttle signal on Cat ET. Verify that the throttle signal is smooth from the low idle position to the high idle position.
Throttle Signal
Result: The throttle signal is OK.
Proceed to Test Step 6.
Result: The throttle signal is NOT OK.
Repair: Troubleshoot and make necessary repairs to the throttle signal.
6. Check the Unit Injectors
A. Use Cat ET to determine if there are any active diagnostic codes for the unit injectors.
B. Perform