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.
Ignition Timing Control: Notes
A microcomputer inside PCM controls ignition timing according to engine speed and vacuum within intake manifold. Engine speed and vacuum are transmitted to PCM by signals from Crankshaft Position (CKP) sensor, Cylinder Position (CYP) sensor, TDC sensor, Throttle Position (TP) sensor, Engine Coolant Temperature (ECT) sensor, Knock Sensors (KS), Mass Air Flow (MAF) sensor, and Manifold Absolute Pressure (MAP) sensor.
PCM calculates ignition timing for each engine speed, manifold pressure, and coolant temperature. When these conditions have been processed, PCM sends signals to Ignition Control Module (ICM) to trigger coil(s).
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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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.