Ignition Monitoring Shunt: Description and Operation

Ignition Coil Diagram:

PURPOSE
The ignition monitoring circuit detects ignition misfire.

OPERATION
The ignition circuit monitoring function detects misfiring on a cylinder-selective basis and discontinues injection to the affected cylinder. Ignition spark output is communicated to the engine control module via a shunt.

The shunt is a 240 ohm resistor in the common secondary ground lead of the ignition coils. If primary ignition circuit monitoring is recognized as OK, but secondary ignition voltage is not reached, the coresponding injector output stage is switched off.