Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Circuit Description
Ignition Control Module (ICM) produces 18X reference signal. ICM calculates 18X reference signal by filtering Crankshaft Position (CKP) sensor 18X pulses when engine is running and CKP pulses are also being received. PCM uses this information to calculate engine speed and CKP at engine speeds less than 1200 RPM. PCM compares number of 18X reference pulses to 3X reference pulses and Camshaft Position (CMP) pulses. DTC will set when, PCM receives incorrect number of pulses or no 18X reference pulses are received in one engine cycle (720 degrees of crankshaft rotation).
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.