- Emission Control System Issues: The check engine light may turn on if the vehicle's emission control system, such as the catalytic converter or oxygen sensors, is not functioning properly.
- Engine Misfire: A misfire in one or more cylinders can trigger the check engine light. Misfires can be caused by a variety of issues, including faulty spark plugs, ignition problems, or fuel injector issues.
- Fuel System Problems: Issues like a clogged fuel filter or a faulty fuel pressure regulator can cause the engine to run lean or rich and trigger the check engine light.
- Oxygen Sensor Issues: Oxygen sensors monitor the oxygen content in the exhaust gas to help control the air-fuel mixture. A faulty oxygen sensor can provide incorrect readings, leading to an illuminated check engine light.
- EVAP System Problems: The evaporative emission control (EVAP) system prevents fuel vapor from escaping into the atmosphere. Issues with the EVAP system, such as leaks or a malfunctioning purge valve, can cause the check engine light to turn on.
- Computer Problems: In some cases, the check engine light may be triggered by a fault in the vehicle's computer or its sensors.
If the check engine light is on in your Toyota Tercel, it is recommended to have the vehicle diagnosed by a qualified technician. They can use specialized diagnostic equipment to accurately identify the root cause of the problem and recommend the necessary repairs. Ignoring or delaying the check engine light can potentially lead to more serious issues and increased repair costs in the future.
