- Identifying Diagnostic Trouble Codes

PRECAUTIONS IN DIAGNOSING FAULTS IN TBI SYSTEM
When diagnosing the Throttle Body Fuel Injection (TBI), the following precautions should be observed:

^ Do not disconnect connectors from the Engine Control Module (ECM), battery cables, ECM ground wire harness, or the 15 amp "TAIL" fuse. Such disconnection will erase ECM Diagnostic Trouble Codes (DTCs) in memory.
^ 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 (spare fuse is connected or the Duty Check Data Link Connector [DLC] is grounded) and ignition switch is in the "ON" position.
^ Note DTC indicated first.
^ 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." When a malfunction can be identified, that is, it is not an intermittent one:
^ Check sensor (actuator), wires and each connection and make sure that they are all in good condition.

When A Malfunction Cannot Be Identified, But The MIL Indicates A DTC:
^ Diagnose malfunctions 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 malfunction 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.