Diagnostic Procedure Description

PURPOSE
Intermittent diagnostic techniques help locate and isolate the root cause of intermittent faults associated with the EEC-V system. The material is organized to help find the fault and perform the repair. There are examples that illustrate the diagnostic techniques. The process of finding and isolating an intermittent, starts with recreating a fault symptom, accumulating PCM data, comparing that data to typical values and analyzing the results.

DESCRIPTION
Diagnosing intermittents can be one of the greatest challenges to the technician. When a symptom is determined to be intermittent, careful visual and physical underhood inspection of:
- connectors
- Wiring harnesses
- Vacuum lines
- Components, etc. is required.
- Vehicle modifications
- Aftermarket items.

A check of any applicable TSBs or OASIS messages may be useful if this information is available. The Customer Information Worksheet may contain more detailed symptom information.
Before an in-depth diagnosis begins, START the engine and wiggle wires, tap on components, etc., while listening for an indication of a problem (example: rpm change, relay clicking).

The Diagnostic Routines Flow Charts may help identify an area of concern. If the Diagnostic Routines Flow Chart(s) have been performed for the reported symptom(s) and no problem is found, go to Pinpoint Test Step Z1. Z1 - Z10

Information about engine conditions is stored when a Diagnostic Trouble Code (DTC) that lights the Malfunction Indicator Lamp (MIL) is set. This information is called Freeze Frame Data and may be helpful in diagnosing intermittents. For more information, refer to Freeze Frame Data Access.