Diagnostic Precautions

PRECAUTIONS IN DIAGNOSING FAULTS IN SEQUENTIAL MULTIPORT FUEL INJECTION SYSTEM

PRECAUTIONS IN IDENTIFYING DIAGNOSTIC TROUBLE CODES
- Do not disconnect connectors from the Engine Control Module (ECM), battery cables, ECM ground wire harness, or the 15 amp "TAIL DOME" Fuse. Such disconnection will erase ECM Diagnostic Trouble Codes (DTCs) in memory.

Multiple DTCs
- If a malfunction lies in two or more areas, the Malfunction Indicator Lamp (MIL) indicates applicable DTCs three times each. These DTCs will flash repeatedly as long as the diagnostic request terminal is grounded (Duty Check Data Link Connector [DLC] is grounded) and ignition switch is in the "ON" position.
- Note DTC indicated first.

Intermittents
- Intermittent malfunctions - There are cases where the MIL indicates a DTC representing a fault which occurred only temporarily and has gone away. In such a case, it may occur that good parts are replaced unnecessarily. To prevent such an error, be sure to follow instructions given below when checking by using the diagnostic charts (A Charts, C Charts, Diagnostic Trouble Code Charts).

Hard Codes
When trouble can be identified, that is, it is not an intermittent one:
- Check sensor (actuator), wires and each connection and if they are all in good condition.

Soft Codes
When a fault cannot be identified, but the MIL indicates a DTC:
- Diagnose fault by using that DTC number and if sensor (actuator), wires and each connection are all in good condition, erase DTC in ECM memory. Then conduct a test run and check what the MIL indicates. Only when it indicates a DTC again, is the fault present.

If it does not indicate a DTC, but normal DTC 12, it means that an intermittent malfunction did occur and has gone away. In this case, check wires and connections carefully again.