For 1990-2009 cars

### Symptom Diagnosis

The Powertrain Control Module (PCM) uses information from the manifold absolute pressure (MAP) sensor, the engine coolant temperature (ECT) sensor, and the engine RPM to calculate the spark advance as follows:

• | A low MAP output voltage = More spark advance

• | A cold engine = More spark advance

• | A high MAP output voltage = Less spark advance

• | A hot engine = Less spark advance

Detonation could be caused by low MAP output or high resistance in the ECT sensor circuit. Reduced 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, the Engine Cranks But Will Not Run diagnostic table must be used to determine if the malfunction is in the electronic ignition system or the fuel system.

If the symptom is an engine miss and the electronic ignition system is suspected, use DTC P0300 for misfire diagnoses.