START FIND THE FAULT 20MINS

1 Read codes

Plug in your code reader, turn on the ignition and scan for stored fault codes. Most OBD systems will identify which coil has failed.

2 Access the coil packs

Our coils fit into the spark plug recesses on top of the cylinder head. Remove the plastic covers over the engine to reveal the cam cover and cylinder head. On this BMW, two covers needed removing.

3 Disconnect wiring

There’s a multi-pin plug which connects to terminals on top of the coil. Lift its metal or plastic retaining clip and unplug the coil pack’s socket. Take care not to strain the wiring.

4 Bolted-up coil pack removal

Some coils, like on this BMW E46, are secured to the engine with two small bolts. Remove the bolts and the coil will pull straight out from the spark plug hole.

5 Push-fit coil pack removal

Our BMW E46 has a later type push fit coil, without securing bolts. Simply pull this up and out of the spark plug hole. If the coil’s rubber boot sticks to a spark plug, retrieve with long-nose pliers.

6 Change the spark plugs

If there’s no record of recent renewal, replace the spark plugs as a matter of course.

7 Fitting the new coil pack

Lightly spray the rubber tip of the new coil with WD40. Press the coil into its recess, making sure the tip engages fully with the top of the spark plug. Refit any securing bolts.

8 Pack wiring

Push the wiring connector back into the socket on top of the coil, making sure it’s fully home before re-engaging the securing clip. Refit any covers that were removed to gain access.

9 Clear the Fault code

Finish by going back to the OBD scanner. From its menu, select ‘Clear Fault Codes’ and press OK. After a few seconds, follow up with another fault code scan, which should show this optimistic message!