Grand Cherokee 2WD L6-4.0L VIN S (1997)
Ignition Coil: Description and Operation
IGNITION COIL
Battery voltage is supplied to the ignition coil positive terminal from the Automatic Shutdown (ASD) relay
The Powertrain Control Module (PCM) opens and closes the ignition coil ground circuit for ignition coil operation.
Base ignition timing is not adjustable on any engine. By controlling the coil ground circuit, the PCM is able to set the base timing and adjust the
ignition timing advance. This is done to meet changing engine operating conditions.
The ignition coil is not oil filled. The windings are embedded in an epoxy compound. This provides heat and vibration resistance that allows the
ignition coil to be mounted on the engine.
CIRCUIT OPERATION
When the Automatic Shut Down (ASD) relay contacts close, circuit A142 supplies voltage to the ignition coil. The Powertrain Control Module
(PCM) controls the ground path for the ignition coil on circuit K19. Circuit K19 connects to cavity A7 of the PCM.
