* Loose or damaged gas cap: This is a frequently overlooked but common cause. A loose or faulty gas cap allows fuel vapors to escape, triggering the light.
* Oxygen sensor malfunction: Oxygen sensors monitor the amount of oxygen in the exhaust. A failing sensor can cause inaccurate fuel mixture, impacting performance and emissions.
* Mass airflow sensor (MAF) issues: The MAF sensor measures the amount of air entering the engine. A dirty or faulty sensor can lead to incorrect fuel delivery.
* Catalytic converter problems: A failing catalytic converter can cause reduced efficiency and emissions problems.
* Spark plugs or ignition coils: Worn spark plugs or failing ignition coils can cause misfires, triggering the check engine light.
* PCV valve problems: A malfunctioning positive crankcase ventilation (PCV) valve can cause excessive crankcase pressure.
* Problems with the engine control module (ECM): The ECM is the "brain" of the engine. Problems with the ECM itself can trigger the light.
* Other sensor issues: Numerous other sensors throughout the engine and emission systems can fail, leading to the check engine light illuminating. These include crankshaft position sensors, camshaft position sensors, and more.
* Low coolant levels: While not directly related to the engine's *function*, low coolant can trigger the light in some vehicles as it relates to the overall system health and emissions.
To determine the *specific* cause, you need to have the OBD system codes read. This can be done by:
* Using an OBD-II scanner: These are readily available at auto parts stores and online. They'll provide a diagnostic trouble code (DTC) which can be looked up to identify the potential problem.
* Taking your Town Car to a mechanic: A mechanic has the tools and expertise to diagnose the issue quickly and accurately.
Ignoring the check engine light is not recommended. Driving with a malfunctioning system could lead to further damage, reduced fuel efficiency, and potentially dangerous driving conditions.
