Malfunction Indicator Lamp: Description and Operation

1997 MIL Change:

OPERATION
1. The malfunction indicator lamp will light up when the ignition switch is turned ON without the engine running. This is a bulb check.
- If the malfunction indicator lamp does not light up, test electrical circuit including bulb.
2. When the engine is started, the malfunction indicator lamp should go off.
If the lamp remains on, the on board diagnostic system has detected an engine system malfunction.

ON BOARD DIAGNOSTIC SYSTEM FUNCTION
The on board diagnostic system has the following four functions.

Diagnostic Test Mode I
1. BULB CHECK: This function checks the MIL bulb for damage (blown, open circuit, etc.).
If the MIL does riot come on, check MIL circuit and ECM test mode selector.
2. MALFUNCTION WARNING : This is a usual driving condition. When a malfunction is detected twice in two consecutive driving cycles (two trip detection logic), the MIL will light up to inform the driver that a malfunction has been detected.
The following malfunctions will light up or blink the MIL in the 1st trip.
- "Misfire (Possible three way catalyst damage)"
- "Closed loop control"
- "Fail-safe mode" [except for crankshaft position sensor (REF) circuit]

Diagnostic Test Mode II
3. SELF-DIAGNOSTIC RESULTS:By using this function, the diagnostic trouble codes can be read.
4. FRONT HEATED OXYGEN SENSOR MONITOR: This function allows the fuel mixture condition (lean or rich) monitored by front heated oxygen sensor, to be read.




MIL Flashing Without DTC
If the ECM is in Diagnostic Test Mode II, MIL may flash when engine is running. In this case, check ECM test mode selector following "HOW TO SWITCH DIAGNOSTIC TEST MODES". How to Switch Diagnostic Test Modes