0123404 JOHNSON PLUG, Ignition switch

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
Complete the procedure in the order in which the steps are listed.
Table 1
Troubleshooting Test Steps Values Results
1. Diagnostic Codes
A. Certain codes may derate engine power. Connect Cat® Electronic Technician (ET) and check for active codes and/or for logged codes.
Diagnostic Codes
Result: A diagnostic code is active or logged.
Repair: 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.
Repair: 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.
Repair: 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.
Repair: 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: 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:
Barometric pressure
Intake manifold air temperature
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: Repair the restrictions or remove the restrictions.