To find out the precise problem, you need to get the diagnostic trouble codes (DTCs) read. There are several ways to do this:
* OBD-II Scanner: This is the most reliable method. You can buy a relatively inexpensive OBD-II scanner at most auto parts stores. Plug it into the car's OBD-II port (usually under the dashboard), and it will read the codes. The codes will be numeric (e.g., P0171, P0420). You can then look up the code's meaning online or in a repair manual.
* Auto Parts Store: Many auto parts stores will read the codes for free. They can then offer advice or parts. Keep in mind they may try to sell you unnecessary repairs.
* Mechanic: A mechanic will have the tools and expertise to diagnose the problem and perform the necessary repairs. This is the most expensive option but often the most reliable.
Possible Causes (without knowing the codes): These are just examples; the actual cause is likely to be different without reading the diagnostic trouble codes:
* Oxygen Sensor: A common culprit in older cars, a failing oxygen sensor can trigger the SES light.
* Mass Airflow Sensor (MAF): This sensor measures the amount of air entering the engine. A faulty MAF can lead to poor fuel mixture and trigger the light.
* Catalytic Converter: Problems with the catalytic converter can cause the SES light to illuminate. This is usually a more expensive repair.
* Evaporative Emission System (EVAP): Leaks in the fuel system can trigger the light.
* Ignition System: Issues with spark plugs, wires, or the distributor (if equipped) could cause a misfire and illuminate the light.
* Loose Gas Cap: While seemingly minor, a loose or damaged gas cap can trigger the SES light because it affects the EVAP system. Try tightening it first, but it likely won't solve underlying issues.
In short: Don't ignore the SES light. Get the diagnostic trouble codes read to determine the specific problem before it worsens or causes more damage.
