Intermittent Problem Diagnosis: Notes

WARNING: This page is about a different car, the 2002 Mercury Villager. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: For additional intermittent fault diagnosis, see TEST Z: INTERMITTENT under SYSTEM TESTS in SELF-DIAGNOSTICS - VILLAGER article.

Intermittent fault testing requires duplicating circuit or component failure to identify the problem. These procedures may lead to PCM setting a DTC which may help in diagnosis.

Intermittent diagnostic techniques help find and isolate root cause of intermittent faults associated with OBD-II system. The process of finding and isolating an intermittent fault starts with recreating the fault symptom, accumulating PCM data and comparing that data to typical values and analyzing the results.

Before proceeding, perform the following:

Customary mechanical system tests and inspections. Ensure they DO NOT reveal a problem. (Remember, mechanical component problems can make a PCM system react abnormally.)
Review all Technical Service Bulletins (TSBs), if available.
QUICK TEST and associated SYSTEM TESTS have been completed without finding a fault, and symptom is still occurring.