Electronic Ignition (EI) System Diagnosis. Chevrolet PJJ 2000

For 1990-2009 cars

### Symptom 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, the technician should refer to Engine Cranks but Does Not Run to determine if the malfunction is in the EI system or the fuel system.

If the symptom is an engine miss and the EI system is suspected, refer to DTC P0300 Engine Misfire Detected .

If DTC P0336 is set, refer to DTC P0336 Crankshaft Position (CKP) Sensor Performance .

### 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.