Exhaust Malfunction Indicator Light (MIL), significance: Notes

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If the Engine Control Module (ECM) recognizes emission related malfunctions, this is indicates by the MIL coming on.

MIL in instrument cluster

Fig 1: Identifying Exhaust Malfunction Indicator Light

Courtesy of AUDI OF AMERICA, INC.

NOTE: When a recognized malfunction switches on the MIL, it will either blink or light continuously. In either case, the DTC memory must be checked. See DIAGNOSTIC TROUBLE CODE (DTC) MEMORY, CHECKING AND ERASING .

Blinking MIL: If the MIL starts to blink, there is a malfunction that can lead to damage of the Three Way Catalytic Converter (TWC). In this case driving should only continue with reduced power until the MIL goes out or stays on continuously.
If the MIL lights continuously, there is malfunction that affects exhaust emissions. In this case the DTC memory of the ECM and Transmission Control Module (TCM) (if equipped) must be checked.
Some malfunctions may occur without causing the MIL to come on. When driveability or performance problems are reported and there is no indication from the MIL, the operation of the MIL must be checked. In addition, the DTC memory of the ECM and TCM must be checked, as there may be malfunctions stored that do not switch the MIL on immediately.