Spark Control System

IGNITION TIMING CONTROL
All ignition timing is controlled by the Powertrain Control Module (PCM); there is no "bypass" mode built into the Ignition Control (IC) module as in other ignition systems.

SPARK ADVANCE CALCULATION
The PCM uses information from the Manifold Absolute Pressure (MAP) and Engine Coolant Temperature (ECT) sensor in addition to RPM to calculate spark advance as follows:

^ Cold engine = More spark advance.
^ Engine under minimum load based on RPM and low amount of air flow = More spark advance.
^ Hot engine = Less spark advance.
^ Engine under heavy load based on RPM and high amount of air flow = Less spark advance.


IGNITION CONTROL SYSTEM
The Ignition Control system consists of the camshaft position sensor, ignition coil, ignition coil module, and PCM. The system connector terminals are identified in Ignition System/Diagrams/Electrical.

IGNITION CIRCUITS
Low Resolution Signal
The low resolution signal reference circuit, CKT 453, provides the PCM with reference signals, firing order, and camshaft position information. If the low resolution signal circuit becomes open or grounded, the engine will not run because the PCM will not operate the ignition coil module, fuel pump, or the fuel injectors. A Diagnostic Trouble Code (DTC) 16 will set if the PCM receives high resolution signal references without the low resolution signals. If engine cranks but will not start, refer to Chart A-3 Engine Cranks But Won't Run. Related Tests, Information and Procedures

High Resolution Signal
The high resolution signal reference circuit, CKT 430, provides the PCM with detailed reference signals and crankshaft position information. If this circuit becomes open or grounded a DTC 36 will set and the engine will still run.

Distributor Reference Low Signal
The distributor reference low signal circuit, CKT 632, is grounded at the PCM and provides a redundant ground for the distributor.

Distributor Ignition Feed
The distributor ignition feed circuit, CKT 631, provides power to the distributor circuity. If this circuit becomes open, the engine will not run since there will be no reference information.

Ignition Control Circuit
The ignition control circuit, CKT 423, controls the ignition coil "ON" and "OFF" time. It signals the ignition coil module to begin primary coil dwell current when the IC is high. The ignition coil module shuts "OFF" ignition coil current when the signal goes low. If this circuit becomes open, shorted to voltage, or grounded, the engine will not start and a DTC 41 or 42 will set.