System Diagnosis

SYSTEM DIAGNOSIS
The PCM uses information from the 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, Chart A-3 must be used to determine if the failure is in the Electronic Ignition (EI) system or the fuel system.

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

DTC PO335
If DTC P0335 is set, that DTC chart 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 DTCs P0301-P0304 for single cylinder misfire diagnosis. If the engine cranks but will not run and the ignition system is suspected, use Chart A-3 Engine Cranks But Will 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.