- Truck Engines:
- C-10 (S/N: 3CS1-UP)
- C-12 (S/N: 2KS1-UP)
- C-15 (S/N: 6NZ1-UP)
- C-16 (S/N: 7CZ1-UP)
- 3406E (S/N: 1MM1-UP; 2WS1-UP)
A 43-02 "Ignition Key Switch Fault" (71) may occur when the ignition key switch is toggled repeatedly within a short time period. For diagnostic purposes, the Engine Control Module (ECM) monitors the key switch circuit for intermittent connections. Some normal operating conditions may cause the 43-02 "Ignition Key Switch Fault" to be logged. Some electronic control modules on the vehicle require the quick cycling of the ignition key switch as a method of requesting diagnostic information.
If the ECM has several logged occurrences of a 43-02 diagnostic code and the operator has not experienced any corresponding symptoms such as intermittent engine shutdowns or engine speed burps, the problem is most likely that someone has rapidly cycled the ignition key switch in order to prompt diagnostic codes from a vehicle control module.
Do not replace the ECM and do not spend excessive time in attempting any diagnosis or repairing the cause of the logged diagnostic codes. Logged 43-02 diagnostic codes that have been generated due to the cycling of the ignition key switch will not cause problems with engine performance. Clear the logged 43-02 diagnostic codes and release the vehicle.