Code 41, OPTI-Spark Ignition System Open Or Shorted Est CKT: Notes

Ignition system provides 2 timing inputs to PCM, high resolution (360 pulses per camshaft revolution) and low resolution (4 pulses per crankshaft revolution). PCM uses these 2 inputs to determine individual spark timing for each cylinder. Once PCM calculates ignition timing, timing signal will be sent to ignition coil driver on EST circuit. Each timing pulse received by ignition coil driver will trigger coil driver to operate ignition coil. EST signal voltage ranges from about .5 volt to 4.5 volts. If a Code 41 is set, PCM will disable fuel injectors to prevent flooding of engine.

1. Determines if code is intermittent.
2. This step determines if EST signal from PCM is available at ignition coil driver. EST circuit voltage should be between about .5 volt and 4.5 volts.
3. Remaining steps ensure coil driver circuitry is okay. If all wiring and connections are okay, check ignition coil and ignition coil voltage supply.