Ignition Coil

The ignition coil (12029) contains three separate ignition coils which are controlled by the ignition control module (ICM) (12K072) through three coil leads.

Each ignition coil fires two spark plugs (12405) simultaneously:

• One spark plug on the compression stroke. This spark plug uses the majority of the ignition coil energy.
• One spark plug on the exhaust stroke. This spark plug uses very little of the ignition coil stored energy.

Since these two spark plugs are connected in series:

• The firing voltage of one spark plug will be negative with respect to ground.
• The voltage of the other will be positive with respect to ground.

Refer to the Powertrain Control/Emissions Diagnosis Manual. for additional information on spark plug polarity.