Electronic Ignition, Description

Electronic Ignition Components

The electronic ignition (EI) system for the 3.4L SHO engine consists of the following components:

crankshaft position sensor (CKP sensor)
camshaft position sensor (CMP sensor)
coil per plug units
the spark control portion of powertrain control module (PCM)
related wiring

Crankshaft Position (CKP) Sensor

Note: Initial engine ignition timing is set at 10 ± 2 degrees BTDC and is not adjustable.

The crankshaft position sensor (CKP sensor) is a variable reluctance sensor, which is triggered by a 36-minus-1 tooth trigger pulse wheel located inside the engine front cover. The sine wave type signal generated from the crankshaft position sensor provides two types of information:

the position of the crankshaft in 10-degree increments.
crankshaft speed (rpm).

Camshaft Position (CMP) Sensor

The camshaft position sensor (CMP sensor):

is a variable reluctance sensor.
is triggered by the high point mark on the LH exhaust camshaft.
provides camshaft rotational location information to powertrain control module (PCM).

The powertrain control module uses the camshaft position (CMP) signal for ignition coil fire sequencing. The powertrain control module also uses the CMP signal for fuel injector synchronization.

Coil Per Plug Unit

The 3.4L SHO engine uses eight separate coil per plug units. Each coil per plug unit is controlled by the powertrain control module (PCM).

Each coil per plug unit is mounted directly above each spark plug and activates its own spark plug in the proper sequence as controlled by the powertrain control module.

Failure Mode Effects Management

During some electronic ignition system concerns, the failure mode effects management portion of the powertrain control module (PCM) will maintain vehicle operation:

If the spark output signal is interrupted, the powertrain control module will automatically turn the coil per plug unit ON and OFF using the CKP signal input. This will result in fixed-spark timing (10 degrees BTDC) and fixed dwell time (no CCD).
If the powertrain control module does not receive the CMP input during engine cranking, random ignition coil synchronization will be attempted from the powertrain control module. Therefore, several start attempts (cycling ignition switch from OFF to START) may be required to start the engine.
if the powertrain control module loses CMP input while the engine is running, the powertrain control module will retain the proper firing sequence and it will continue to fire the coil per plug units to maintain engine operation.

Ignition Diagnostic Monitor

The ignition diagnostic monitor is a function of the powertrain control module (PCM). The powertrain control module stores the information for use during diagnostic test mode.

Contact Information