Malfunction Indicator Lamp (MIL) Significance

Malfunction Indicator Lamp, Significance

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





Malfunction Indicator Lamp (MIL) For Exhaust

NOTE:
Exhaust MIL can be switched on with a blinking or steady light DTC memory must be checked in either case.
- Blinking: There is a malfunction that damages the catalytic converter at this driving condition (e.g. combustion misfire). In this case, vehicle must only be driven at reduced power!
- Steady light. There is a malfunction that worsens the exhaust. Check DTC memory for motronic ECM and Transmission Control Module (if installed).
- If there are driveability problems or if there is a customer complaint and the exhaust MIL is not lit, DTC memory must be checked. There may be DTCs stored that do not cause the exhaust MIL to light immediately, but only if malfunction is recognized again after repeated engine starts.

Function test
- Switch ignition on:
- Exhaust MIL must light.

If exhaust MIL does not light when ignition is switched on:
- Check wire from ECM to exhaust MIL as follows:

Cause: Remedy:
Exhaust MIL is not being activated - Switch ignition off.
or does not light due to open circuit. - Connect VAG 1598/31 test box.
- Bridge sockets 2 and 47 of test box.
- Switch ignition on.
Exhaust MIL must light.
If exhaust kill does not light:
- Switch ignition Off.
- check bulb in Malfunction Indicator Lamp (MIL) (burnt out)
- Check voltage supply of lamp per wiring diagram
If lamp is OK and voltage supply is present:
- Locate short circuit or open circuit from ECM to Malfunction Indicator Lamp (MIL) and repair.
If no malfunctions are found in wire to exhaust MIL:
Malfunction cause ECM malfunctioning, Replace ECM.

If exhaust MIL does not light when ignition is switched on, continue test as follows:
- Start engine and run at idle:
- Exhaust MIL must go out after a few seconds.

If exhaust MIL does not go out:
- Check DTC Memory.

If there are no DTCs are stored:

Cause: Remedy:
Exhaust MIL is being constantly activated - Switch ignition off.
by short circuit to Ground (GND). - connect VAG 1598/31 test box
- Measure wire resistance between socket 47 of test box vehicle Ground (GND).
Specification: Infinite ohm (Infinite ohm)
If specified value is not obtained:
Short circuit to Ground (GND) in activation wire from ECM to exhaust MIL.
- Locate malfunction and repair per wiring diagram.
If Specified value Infinite ohm (Infinite ohm) is obtained, and no short circuit to Ground (GND) is found:
Malfunction cause ECM malfunctioning, replace ECM.