Circuit Description
WARNING: This page is about a different car, the 2003 Lexus SC 430. However, it is still accessible from the selected car via links, so may be relevant.
ECM uses the crankshaft position sensor and camshaft position sensor to monitor changes in the crankshaft rotation for each cylinder. ECM counts the number of times the engine speed change rate indicates that misfire has occurred. When misfire rate equals or exceeds count of indicating that engine condition has deteriorated, MIL lights up. If misfire rate is high enough and the driving conditions will cause the catalyst to overheat, MIL blinks when misfiring occurs. See Fig 1. Possible causes are:
- Open or short in wiring.
- Poor connector contact at ECM.
- Vacuum hose leaking or misrouted.
- Faulty ignition system.
- Faulty fuel injector(s).
- Improper fuel pressure.
- Faulty Mass Airflow (MAF) sensor.
- Faulty Engine Coolant Temperature (ECT) sensor.
- Faulty engine compression.
- Improper valve clearance.
- Improper valve timing.
- PCV hose connection.
- Faulty ECM.