Malfunction Indicator Lamp (MIL), Operation

Malfunction Indicator Lamp, significance

If malfunctions which adversely affect exhaust emissions are recognized by the ECM, they will be communicated to the instrument cluster through the CAN-Bus and indicated by the Malfunction Indicator Lamp (MIL) switching ON.







Location of MIL lamp

1 - MIL lamp
2 - Glow plug indicator light


NOTE: The Glow plug indicator light has a dual function:

- Blinking: A malfunction has been recognized which affects handling. Stored malfunctions can be displayed by either the VAG1551 or VAG1552 Scan Tool.
- The MIL lamp must light up when when the ignition is switched ON: this is a normal function when starting a cold Diesel engine.

The MIL lamp is switched ON when malfunctions are recognized which adversely affect exhaust emissions. If this happens, check DTC memory. Reading Diagnostic Trouble Codes

Functional check
- Switch ON ignition
- MIL lamp must light up until engine starts.
- The Glow plug indicator light can also light up during the pre-glow period if the engine is cold.

If MIL lamp does not light-up with ignition switched ON:
- Check MIL lamp wiring / MIL lamp bulb using wiring diagram.

If OK:
- Check instrument cluster / ECM and replace.
- Erase DTC memory. With Manufacturer's Scan Tool
- Set Readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

If the MIL lamp lights-up with ignition switched on, continue check as follows:
- Start engine and let idle
- MIL lamp must switch OFF after a few seconds.

If MIL lamp does not switch OFF:
- Check DTC memory. If no malfunction stored: Reading Diagnostic Trouble Codes
- Check MIL lamp using wiring diagram.

If OK:
- Check instrument cluster / ECM and replace.
- Erase DTC memory. With Manufacturer's Scan Tool
- Set Readiness code. Monitors, Trips, Drive Cycles and Readiness Codes