General Information

Ignition System:

The PCM uses reference pulses from the CMP sensor in order to determine engine speed. The PCM cannot operate the ignition system - or the fuel injectors - without the engine speed signal from the CMP.

The four ignition coils supply spark to each engine cylinder (spark plug) at precisely the right time. When the PCM signals the ignition coil's built-in ignition module to interrupt the current flow in the primary coil windings, the electrical field around the primary coil collapses and a high voltage is induced in the secondary coil. The secondary coil voltage travels unhindered to the spark plug, through the high voltage output terminal and boot assembly.

The PCM also uses the CMP sensor signal as an input for control of the fuel injectors and ignition timing. The CKP sensor signal is used by the PCM for engine misfire detection.

The PCM provides three modes of ignition timing control. Each ignition timing mode provides the most suitable spark advance for optimal engine performance. The following are the 3 modes of ignition timing control:
^ Initial Timing Control (at engine start) - The Initial Timing Control ignition advance provides better starting performance of the engine at start-up, when engine speed is less than 500 RPM. The PCM sets initial ignition timing advance to 5 degrees BTDC.
^ Basic Timing Control (after engine start) - After the engine is running, ignition timing advance is determined by combining Basic Timing Control and Compensating Timing Control. Basic Timing Control ignition advance is based on engine coolant temperature, engine speed, and intake air volume. The ignition timing advance value, calculated from the ECT sensor, the CMP sensor, and the MAF sensor input, is added to the 5 degrees initial advance, and modified by the Compensating Timing Control value.
^ Compensating Timing Control - The Compensating Timing Control ignition advance is added to the Basic Timing Control value and varies according to engine and vehicle conditions. The most important factors in calculating the compensating ignition advance value are engine coolant temperature, intake air temperature, and engine idling demands.

Ignition timing on the 2.0L engine is adjustable. The CMP sensor housing can be repositioned, much like a distributor, in order to adjust the base ignition timing setting. A scan tool must be used to request that the PCM operate the ignition system in the ignition timing check mode. Refer to Ignition Timing Adjustment in Computers and Controls.