Common Issues (More likely at higher mileage):
* Oxygen Sensor(s): These sensors monitor the exhaust gases and help regulate fuel efficiency. A faulty sensor is a very common cause of a check engine light.
* Mass Airflow Sensor (MAF): This sensor measures the amount of air entering the engine. A dirty or failing MAF sensor can lead to poor fuel mixture and illuminate the light.
* Catalytic Converter: These converters break down harmful emissions. A failing converter can be expensive to replace.
* Spark Plugs/Wires: Worn or damaged spark plugs and wires can cause misfires, leading to the light.
* Ignition Coil: A faulty ignition coil can prevent proper sparking in one or more cylinders.
* PCV Valve (Positive Crankcase Ventilation): This valve helps to vent gases from the crankcase. A clogged PCV valve can cause various problems.
* Throttle Position Sensor (TPS): This sensor monitors the throttle's position. A faulty TPS can lead to erratic idling and power delivery issues.
* Low Coolant Level: While not directly a sensor issue, a low coolant level can trigger the light in some vehicles.
Less Common, But Possible:
* Sensor Failures: Many other sensors (crankshaft position sensor, camshaft position sensor, etc.) can cause the light to illuminate.
* Exhaust Leaks: A leak in the exhaust system can affect the oxygen sensor readings.
* Transmission Issues: In some cases, transmission problems can trigger the check engine light.
To find the specific cause:
You need to get the diagnostic trouble codes (DTCs) read from the car's onboard computer. This can be done in a few ways:
* OBD-II Scanner: Purchase a relatively inexpensive OBD-II scanner from an auto parts store. These scanners will read the codes and often provide descriptions of the likely problems.
* Auto Parts Store: Many auto parts stores will read the codes for free.
* Mechanic: A mechanic will be able to read the codes and diagnose the problem.
Once you have the DTCs, you can look them up online or in a repair manual to get a better understanding of the potential issue. This is crucial for effective troubleshooting. Don't just guess based on the light alone; a proper diagnosis is needed to fix the problem correctly.
