Diagnostic System Check

ON-BOARD DIAGNOSTIC SYSTEM CHECK
The "On-Board Diagnostic System Check" is an organized approach for identifying a problem caused by the on-board computer controlled systems. Understanding this chart and using it correctly will reduce diagnosis time and prevent the unnecessary replacement of parts. If you have not reviewed the basic information on how to use the computer self-diagnostics, go to the beginning of this section.

NOTES ON TROUBLE TREES
1. If diagnostic system is not functional, a problem might be present in the ACAC or related system. (This could mean that the diagnostic system has detected a problem in the data line that connects all of the computer systems together. This will also stop all Tech 1 communication.
2. If diagnostic trouble codes are present, they should be diagnosed in the order shown for that system.
3. If no diagnostic trouble codes are present, then refer to Symptom or System Charts in the system exhibiting the condition.