Ignition Control

The ignition control (1C) spark timing is the ECM's method of controlling the spark advance and the ignition dwell.

The 1C spark advance and the ignition dwell are calculated by the ECM using the following inputs:

• Engine speed.
• Crankshaft position (58X reference).
• Engine coolant temperature (ECT) sensor.
• Throttle position (TP) sensor.
• Park/Neutral position (PRNDL input).
• Vehicle speed (vehicle speed sensor).
• ECM and ignition system supply voltage.

Fig 1: Removing Bolts Of Ignition Control

Courtesy of ISUZU MOTOR CO.

Based on these sensor signals and engine load information, the ECM sends 12V to each ignition coil.

Fig 2: Identifying Sensor Signals And Engine Load Information

Courtesy of ISUZU MOTOR CO.

This module has the function to energize and de-energize the primary ignition coil in response to signals from the ECM. The ECM 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.

Fig 3: Identifying Electronic Spark Timing

Courtesy of ISUZU MOTOR CO.