Ignition Control - Spark Timing Description

Ignition Control
The ignition control (IC) spark timing is the PCM's method of controlling the spark advance and the ignition dwell.

The IC spark advance and the ignition dwell are calculated by the PCM using the following inputs:
- Engine speed.
- Crankshaft position (58X reference).
- Camshaft position (CMP) sensor.
- Engine coolant temperature (ECT) sensor.
- Throttle position (TP) sensor.
- ION sensing module.
- Park/Neutral position (PRNDL input).
- Vehicle speed (vehicle speed sensor).
- PCM and ignition system supply voltage.




- The crankshaft positron (CKP) sensor sends the PCM a 58X signal related to the exact position of the crankshaft.
- The camshaft position (CMP) sensor sends a signal related to the position of the camshaft.




Based on these sensor signals and engine load information, the PCM sends 5 V to each ignition coil.

This module has the function to energize and de-energize the primary ignition coil in response to signals from the PCM. The Throttle PCM controls ignition timing and dwell time.

Continuity and out-or-range value check:

This diagnosis detects open circuit or short-circuiting in the Electronic Spark Timing (EST) line by monitoring EST signals. A failure determination is made when the signal voltage remains higher or lower than the threshold for corresponding fault code beyond a predetermined time period.




Diagnosis enabling conditions are as follows:
- RPM is higher than the specified threshold.
- EST line is enabled.