System Diagnosis - Electronic Ignition

Symptom Diagnosis

The PCM uses information from the Manifold Absolute Pressure (MAP) and coolant sensors in addition to RPM to calculate spark advance as follows:

^ Low MAP output voltage = More spark advance.

^ Cold engine = More spark advance.

^ High MAP output voltage = Less spark advance.

^ Hot engine = Less spark advance.

Detonation could be caused by low MAP output or high resistance in the Engine Coolant Temperature (ECT) sensor circuit. Poor performance could be caused by high MAP output or low resistance in the coolant sensor circuit.

If the engine cranks but will not run or immediately stalls, Engine Cranks but Does Not Run must be used to determine if the failure is in the EI system or the fuel system.

If the symptom is an engine miss and the El system is suspected, use DTC P0300 for multiple cylinder misfire and DTC's P0301-P0304 for single cylinder misfire.


DTC P0335

If DTC P0335 is set, that DTC table must be used for diagnosis. If the symptom is Engine Misses and the ignition system is suspected, use DTC P0300 for multiple cylinder misfire and DTC's P0301-P0304 for single cylinder misfire diagnosis. If the engine cranks but will not run and the ignition system is suspected, use Engine Cranks but Does Not Run.


Setting Timing

Because the reluctor wheel is a precision machined part of the crankshaft and the Crankshaft Position (CKP) sensor is mounted in an accurately located, fixed position, timing adjustment is not possible or necessary.