Ignition Coil: Description and Operation
IGNITION COILThe ignition coil assembly for the 4 cylinder engines consists of 2 or 3 independent coils molded together. The coil assembly for the 4 cylinder engines is mounted on the cylinder head cover. Spark plug cables route to each cylinder from the coil.
The coil for the 4 cylinder engines fires two spark plugs every power stroke. One plug is the cylinder under compression, the other cylinder fires on the exhaust stroke. The Powertrain Control Module (PCM) determines which of the coils to charge and fire at the correct time.
The Auto Shutdown (ASD) relay provides battery voltage to the ignition coil. The PCM provides a ground contact (circuit) for energizing the coil. When the PCM breaks the contact, the magnetic energy in the coil transfers to the secondary causing the spark. The PCM will de-energize the ASD relay if it does not receive the crankshaft position sensor and camshaft position sensor inputs. Refer to Auto Shutdown (ASD) Relay-PCM Output, for relay operation.