Malfunction Indicator Lamp (MIL), significance

WARNING: This page does not describe the selected car, but rather 15 other vehicles, including the 1999 Volkswagen Jetta, 1999 Volkswagen Golf, 1999 Volkswagen Cabrio, 1998 Volkswagen Jetta, and 1998 Volkswagen Golf. However, it is still accessible from the selected car via links, so may be relevant.

If malfunctions are recognized and verified by the engine control module, they will be indicated by switching on the malfunction indicator lamp.

Location of malfunction indicator lamp (MIL)

Fig 1: Identifying Location Of Malfunction Indicator Lamp (MIL)

NOTE: The MIL can be switched on in the flashing or permanently on mode. The Diagnostic Trouble Code (DTC) memory must be checked in every case. See Check DTC Memory (scan tool function 02) .

Flashing: There is a malfunction that can damage the Three Way Catalytic Converter (TWC) if driven in this condition. In this case, the vehicle must not be driven using wide open throttle, but with partial throttle only, during which the MIL is continuously illuminated rather than flashing.
Permanently on: There is a malfunction which will increase exhaust emissions. Check engine and/or automatic transmission control modules.
If the MIL does not light up: If there is an engine running problem, or a customer complaint of one, perform a functional check of the MIL. Then DTC memory must be checked because malfunctions that do not switch on the MIL immediately can also be stored.

Functional check:

Switch ignition on:
- The MIL must light -up.

If the MIL does not light-up with ignition switched on:

Check wiring to MIL as follows.

MIL DOES NOT LIGHT-UP WITH IGNITION SWITCHED ON

Cause:	Remedy:
MIL is not activated or does not light-up due to open circuit	Switch ignition off Connect test box VAG 1598/18 Bridge test box sockets 1 and 3 Switch ignition on MIL must light-up If the MIL does not light-up: Switch ignition off Check bulb in the MIL If bulb is OK: Locate and eliminate short or wiring open circuit from Engine Control Module (ECM) to MIL using wiring diagram
Malfunction cause:	If no malfunction can be detected in the wiring to MIL: ECM -J220- faulty Replace ECM, erase Diagnostic Trouble Code (DTC) memory

Cause:

Remedy:

MIL is not activated or does not light-up due to open circuit

Switch ignition off
Connect test box VAG 1598/18
Bridge test box sockets 1 and 3
Switch ignition on
- MIL must light-up

If the MIL does not light-up:

Switch ignition off
Check bulb in the MIL

If bulb is OK:

Locate and eliminate short or wiring open circuit from Engine Control Module (ECM) to MIL using wiring diagram

Malfunction cause:

If no malfunction can be detected in the wiring to MIL:
ECM -J220- faulty

Replace ECM, erase Diagnostic Trouble Code (DTC) memory

If the MIL lights-up with ignition switched on, continue check as follows:

Start engine and run at idle speed.
- The MIL must go out after a few seconds.

If the MIL does not go out:

Check DTC memory: See Check DTC Memory (scan tool function 02) .

If no malfunction is stored:

MIL DOES NOT GO OUT - NO MALFUNCTION IS STORED

Cause:	Remedy:
MIL is permanently activated by short circuit to Ground (GND)	Switch ignition off Connect test box VAG 1598/18 Check resistance between test box socket 3 and vehicle Ground (GND), specification: INFINITE ohms (Ω) If the specification is not attained: Short circuit to (GND) in the activation wire from Engine Control Module (ECM) -J220- to MIL Locate and eliminate this malfunction using wiring diagram
Malfunction cause:	If the specification INFINITE ohms (Ω) is attained and no short circuit to (GND) can be found: ECM -J220- faulty Replace ECM, erase Diagnostic Trouble Code (DTC) memory

Cause:

Remedy:

MIL is permanently activated by short circuit to Ground (GND)

Switch ignition off
Connect test box VAG 1598/18
Check resistance between test box socket 3 and vehicle Ground (GND), specification: INFINITE ohms (Ω)

If the specification is not attained:

Short circuit to (GND) in the activation wire from Engine Control Module (ECM) -J220- to MIL

Locate and eliminate this malfunction using wiring diagram

Malfunction cause:

If the specification INFINITE ohms (Ω) is attained and no short circuit to (GND) can be found:
ECM -J220- faulty

Replace ECM, erase Diagnostic Trouble Code (DTC) memory