1. Loose or Faulty Gas Cap: A loose or faulty gas cap can cause the check engine light to turn on. Ensure the gas cap is tightened securely after refueling.
2. Oxygen Sensor Issues: A faulty oxygen sensor can cause the check engine light to illuminate. This sensor measures the amount of oxygen in the exhaust, and if it's not functioning correctly, it can impact fuel efficiency and emissions.
3. Catalytic Converter Problems: Issues with the catalytic converter, which helps reduce harmful emissions, can also trigger the check engine light.
4. Faulty Spark Plugs or Ignition Coils: Malfunctioning spark plugs or ignition coils can cause misfires, leading to the check engine light turning on.
5. Evaporative Emissions System Issues: Problems with the evaporative emissions system, which captures and stores fuel vapors to prevent their release into the atmosphere, can cause the check engine light to illuminate.
6. Transmission Problems: If your Tercel has an automatic transmission, issues such as low transmission fluid levels or faulty transmission sensors can cause the check engine light to turn on.
7. Electrical Issues: Electrical problems, such as faulty wiring or malfunctioning sensors, can also trigger the check engine light.
8. ECM (Engine Control Module) Issues: The ECM is the vehicle's computer that controls various engine functions. Malfunctions or software glitches within the ECM can cause the check engine light to illuminate.
If the check engine light turns on and off intermittently in your 1994 Toyota Tercel, it's important to have the vehicle diagnosed by a qualified mechanic to identify the specific cause. Driving with the check engine light on can potentially indicate a more serious underlying issue that requires attention.
