With Manufacturer's Scan Tool

Exhaust Malfunction Indicator Lamp (MIL) In Instrument Cluster

If the ECM recognizes malfunctions that lead to a worsening of emissions values, it indicates them by lighting the exhaust Malfunction Indicator Lamp (MIL).

The Engine Control Module (ECM) switches on the exhaust Malfunction Indicator Lamp (MIL) after ignition is switched on. Shortly after engine is started, the exhaust MIL will go out. This requires, first of all, that the Engine Control Module (ECM) does not detect a malfunction that worsens the emissions values and, secondly, that activation of the lamp by the Engine Control Module (ECM) is OK.

If malfunctions that worsen emissions are recognized during operation of the engine, the ECM switches on the exhaust MIL in instrument cluster. An entry is made in DTC memory at the same time.

The Malfunction Indicator Lamp (MIL) can blink or remain lit continuously. DTC memory should be checked in either case. Diagnostic Trouble Code (DTC) Memory, Checking

Continuously lit:
There is a malfunction that causes increased emissions. Check DTC memory for Motronic ECM and automatic transmission (if installed).

Check DTC memory if there is a drivability problem or a customer complaint, but the exhaust Malfunction Indicator Lamp (MIL) is not lit. There may be DTCs stored that do not cause the exhaust MIL to light up immediately, but only after engine is started again and malfunction is recognized again.

Blinking:
There is a malfunction that causes damage to the catalytic converter in this driving condition (e.g. combustion misfire). In this case, vehicle must only be driven at reduced power.