* Loose or bad gas cap: This is a common and easily fixable cause. A loose or faulty gas cap allows fuel vapors to escape, triggering the light.
* Oxygen sensor malfunction: The oxygen sensor measures the amount of oxygen in the exhaust. A faulty sensor can affect fuel efficiency and emissions, triggering the light.
* Mass airflow sensor (MAF) problem: The MAF sensor measures the amount of air entering the engine. A dirty or faulty sensor can lead to inaccurate fuel mixture and trigger the light.
* Spark plug or ignition coil issues: Problems with spark plugs or ignition coils can cause misfires, leading to the service engine light illuminating.
* Catalytic converter failure: A failing catalytic converter can impact emissions and trigger the light. This is a more expensive repair.
* Other sensor problems: Numerous other sensors (e.g., crankshaft position sensor, camshaft position sensor, temperature sensors) can malfunction and trigger the light.
* Low coolant level: While not always directly triggering the light, low coolant can indicate a leak and potentially cause overheating, which might indirectly trigger a related warning light.
* Transmission issues: Problems with the transmission can sometimes activate the service engine light, although other transmission-specific warning lights might also appear.
To diagnose the problem:
1. Check the gas cap: Make sure it's tight and not damaged.
2. Use an OBD-II scanner: This inexpensive tool can read the diagnostic trouble codes (DTCs) stored by the car's computer. The DTCs provide a clue to the specific problem.
3. Consult a repair manual: A repair manual specific to your Cavalier year and model can provide troubleshooting steps for various codes.
4. Take it to a mechanic: If you can't identify the problem with an OBD-II scanner and repair manual, a qualified mechanic can diagnose and fix the issue.
Ignoring a constantly illuminated service engine light can lead to further damage and potentially unsafe driving conditions. It's crucial to address the underlying problem.
