Systematic Troubleshooting

Once a malfunction has been verified, troubleshooting should be devoted to finding the cause of the problem, then correcting the fault; only if the cause is positively identified can the vehicle be confidently released to the customer.



Remember that the vast majority of causes for complaint concerning electronically-controlled systems are not exotic electronic malfunctions; rather, the cause is almost always a simple electrical fault, such as an open circuit, a short circuit (to B+ or B-), or excessive resistance (poor contact).


If the faulted system is equipped with self-diagnostics, the first step should be to call up any flash codes (for systems - without the diagnostic link) or to read out the control module's fault memory (for systems with the diagnostic link). Read out and print the contents of all systems' fault memories.


Refer to the appropriate Electrical Troubleshooting Manual and examine the schematics of the system circuitry. If several systems are faulted, common or shared circuits may provide a clue that will aid in more efficient diagnosis.






On systems which have no self diagnostic capabilities (or on any self-diagnostic systems which does not provide clear evidence of a fault location), an examination of all circuits of the system should be performed. Installation of the appropriate adapter ("break-out box") between the control module and harness will allow the technician to monitor the electrical activity at each pin of the control module.