General Diagnostic Procedure

General Diagnostic Procedure

If the initial inspection and any subsequent repairs do not correct the problem, follow this general diagnostic procedure to determine the fault and correct the problem:

1. Record And Clear All EMS DTCs.
Use JDS or PDU to retrieve and note all of the diagnostic trouble codes from the ECM memory. On 1993 and 1994 model year vehicles, JDS will print the number of failures that have been detected, as well as certain fault details (e.g.; intermittent or present, short circuit or open circuit). Record this information.
To clear the codes, use JDS or PDU. If the power supply to the ECM is disconnected, all DTCs are cleared and cannot be retrieved.
If JDS or PDU is not available, DTCs can be retrieved and cleared one by one using the DTC reset connector.

2. Operate The Vehicle And Determine If The Fault Still Exists.
Refer to the Engine Management Customer Questionnaire and/or any applicable DTC Fault Diagnosis Procedures. Note the "Conditions required for DTC flagging". Operate the vehicle and try to reproduce the conditions that cause the complaint or DTC.
If a fault occurs or if a DTC is reflagged, the fault is still present and can probably be identified quickly using PDU or a DVOM to monitor the system while driving.
If a fault does not occur or if a DTC was originally stored and is not reflagged, the fault is intermittent. Visually inspect the systems and circuits listed as possible faults.

3. Test And Repair The Systems And Circuits.
Refer to the Fault Finding Matrix on page 10 and/or the applicable Fault Diagnosis Procedures. Test the indicated systems or circuits. Use PDU while driving to check for dynamic faults. Determine the required repairs.
If more than one DTC is flagged, investigate the highest priority code first.
Test the suspect systems and components using the information provided.
Carry out repairs as necessary.

4. Retest The Vehicle.
Upon completion of repairs, retest the vehicle as described in step 3 above.