Malfunction Indicator Lamp (MIL), significance

The Malfunction Indicator Lamp (MIL) lights up when malfunctions are recognized by the Engine Control Module (ECM).

Fig 1: Locating Malfunction Indicator Lamp

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Installation position of exhaust MIL

• Blinking: There is a malfunction that damages the catalytic converter in this driving condition. In this case, vehicle must only be driven at reduced power!
• Steady light: There is a malfunction that causes increased emissions. Check DTC memory for Motronic ECM or automatic transmission.
• DTC memory must still be checked if there are driveability problems or the customer has made a complaint but the MIL is not lit, because malfunctions can be stored without causing the MIL to light immediately.

Function test: 

• Switch on ignition:

exhaust MIL must light.

If exhaust MIL does not light when ignition is switched on:

• Check instrument cluster and Malfunction Indicator Lamp (MIL) as follows:

Refer to 01 ON BOARD DIAGNOSTIC (OBD)

If exhaust MIL does not light when ignition is switched on, continue test as follows:

• Start engine and let run at idle:

Exhaust MIL must go out after a few seconds.

If exhaust MIL does not go out:

• Check DTC memory, repair any malfunctions and then erase DTC memory. Refer to DTC memory of Engine Control Module (ECM), checking (scan tool function 02) and erasing (scan tool function 05)  , Erasing and checking DTC memory.
• Read readiness code. Refer to Readiness code, checking  . If DTC memory was erased or the Engine Control Module (ECM) was disconnected from continuous B+ supply, readiness code must be re-generated. Refer to Readiness code, generating  .