Ignition Coils, Checking

Ignition Coils, Checking

NOTE: The ignition coil and output stage form one joint component.

Condition
- No fault relating to injector(s) stored

Determine non-operating/misfiring cylinder as follows:
- Check misfiring recognition. Testing and Inspection

If misfiring detected:
- Continue testing at cylinder indicated see "Once faulty cylinder determined".

If misfiring not detected:
- Remove air cleaner housing to gain access to injectors (Engine is operated briefly without mass air flow sensors; this is not a problem for the short period of time involved).

NOTE: The greatest possible care must be taken to prevent objects falling into the intake connections to the turbochargers.

- Consecutively disconnect connectors of injectors with engine running and observe engine operation.
or
- Compare spark plugs of all cylinders and look for soot deposits on electrodes.

Once faulty cylinder is determined:
- Swap spark plug of faulty cylinder with that of another cylinder.

If fault accompanies spark plug:
- Replace spark plug.

If fault remains with cylinder:
- Swap ignition coil of faulty cylinder with that of another cylinder.
- If fault now occurs at other cylinder, replace ignition coil.

If fault remains with cylinder, check ignition coil Ground wire.

Checking ignition coil Ground wire
- Disconnect 4-pin connector at relevant ignition coil.







- Check for open circuit and short to positive in Ground connection from socket 4 of 4-pin connector to engine Ground.
- Eliminate open circuit in wiring/short circuit if necessary.

If Ground connection is OK:
- Check power supply of ignition coil.

Checking power supply of ignition coil







- Connect portable multimeter for voltage measurement to following connector socket.
- Switch on ignition.

4-pin connector at wiring Specification
harness, socket
1 + Ground Battery voltage

Specification: approx. battery voltage

If reading does not match specification:

- Check for continuity in wiring from socket 1 via fuse to Motronic ECM power relay -J271- and repair if necessary.
- Check Motronic ECM power supply relay -J271.

If reading matches specification:
- Check output stage. Ignition Coil Output Stages, Checking