Diagnostic Circuit Check

Flow Of Diagnosis:

NOTE:
a. Numbers below refer to circled numbers in flow chart.
b. Since this is the starting point for all diagnostic procedures or finding the cause of an emissions test failure, always begin here and always follow the flow chart as directed.
c. For trouble code diagnosis and Charts A-1 and A-2, refer to COMPUTERIZED ENGINE CONTROLS.

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.

Perform Underhood Inspection:

a. Check vacuum hoses for splits, kinks, and proper routing.
b. Check ignition wires for cracking, hardness, and proper connections at both the distributor and spark plugs.
c. Check all wiring for proper connections, pinches, and cuts.
d. Check wiring harness for proper routing.
e. Check for missing components.

2. Check for manual updates, testing procedures, warranty and recall information.

3. Refer to COMPUTERIZED ENGINE CONTROLS/PROM I.D.

4. Perform the system check. The system check is performed through the twelve terminal assembly line data link (ALDL) connector under the instrument panel in the passenger compartment.

The Computer Command Control System Check is a procedure that determines the following:

a. Bulb Check - to check Service Engine Soon (SES) light circuit and that the ECM can complete the circuit.
b. Diagnostic Mode - this indicates if the diagnostic code system is working.
c. Scan Data - this determines if the ECM is supplying input and output visual data.
d. Engine Start - this step is done after it has been determined that the ECM will display codes and data.
e. Other Codes - Proceed to the applicable chart if a code is displayed. Scanning the data for typical values may indicate if they are incorrect. If all systems appear to be functioning, refer to DIAGNOSIS BY SYMPTOM in COMPUTERIZED ENGINE CONTROLS

5. Refer to COMPUTERIZED ENGINE CONTROLS/DIAGNOSIS AND TESTING/DIAGNOSTIC CHARTS/A-CHARTS.

6. Refer to DIAGNOSIS AND TESTING/DIAGNOSTIC CHARTS/A-CHARTS.

7. At this point it would be advantageous to know if the problem is ignition related or other. Choose the path that best suits the individual situation.