1. Oxygen sensor: A faulty oxygen sensor can cause the check engine light to turn on. This sensor measures the amount of oxygen in the exhaust gases and helps regulate the fuel-air mixture.
2. Catalytic converter: A failing catalytic converter can also trigger the check engine light. This component helps convert harmful pollutants in the exhaust gases into less harmful substances.
3. Mass airflow sensor: The mass airflow sensor measures the amount of air entering the engine. If it's malfunctioning, it can affect the engine's performance and cause the check engine light to come on.
4. Spark plugs or ignition coils: Worn-out spark plugs or faulty ignition coils can lead to misfires and cause the check engine light to illuminate.
5. Evaporative emissions control system (EVAP): Issues related to the EVAP system, which controls fuel vapors, can cause the check engine light to come on.
6. Engine oil pressure: Low oil pressure or a faulty oil pressure sensor can also trigger the check engine light.
7. Transmission problems: In some cases, transmission-related issues, such as slipping gears or solenoid failures, can cause the check engine light to turn on.
8. Faulty sensors or modules: Various other sensors or modules in the vehicle, such as the throttle position sensor, knock sensor, or fuel level sensor, can malfunction and cause the check engine light to come on.
To accurately identify the cause of the check engine light in your 2003 Lexus ES, it's best to have it diagnosed by a professional mechanic or a certified Lexus dealership. They can use diagnostic tools to scan the vehicle's computer system and pinpoint the specific issue.
