- Flow of Diagnosis - Start Here

Flow Of Diagnosis:

This flow of diagnosis is designed to help guide technicians in diagnosing problems related to control devices and systems,

Verify that the problem exist and verify whether the problem is a intermittent or a constant problem. DO NOT use the A-CHARTS or TROUBLE CODE CHARTS for diagnosis of intermittent problems.

NOTE:: For further information, use the DRIVEABILITY WORKSHEET and the VEHICLE REPAIR HISTORY forms under INFO TYPE MENU / TECHNICAL MANAGEMENT SUPPORT / SERVICE CONSULTANT under the main menu.


Numbers below refer to circled numbers in flow chart.

1. Get an accurate description of the complaint and verify. Include filling out the DRIVEABILITY WORKSHEET and VEHICLE REPAIR HISTORY. Refer to INFO TYPE/TECHNICAL MANAGEMENT SUPPORT for forms.

2. Perform Underhood Inspection:
A careful visual inspection can often locate the source of a problem without further testing.

^ Check vacuum hoses for splits, kinks, and proper routing.
^ Check all wiring for proper connections, pinches, and cuts.
^ Check wiring harness for proper routing.
^ Check for missing components.

3. Check for manual updates, testing procedures, warranty and recall information. There may be a factory update that directly addresses the customers complaint.

4. Perform the DIAGNOSTIC CIRCUIT CHECK under TESTING PROCEDURES. This checks to make sure that the computer is functioning properly and that the "SERVICE ENGINE SOON LIGHT" is working. This is the starting point for the diagnosis of the problem, and this circuit check will direct you to the proper test procedure.


5. If there are no trouble codes, Refer to Diagnosis By Symptom Testing and Inspectionfor help identifying systems or components that could cause an emission test failure without setting codes.