Here's what you should do:
1. Get the Diagnostic Trouble Code (DTC): This is the crucial first step. You need to know *why* the light is on. You can do this in a few ways:
* OBD-II Scanner: The most reliable method. Buy a relatively inexpensive OBD-II scanner from an auto parts store (many are under $30). Plug it into the OBD-II port (usually under the dashboard) and it will read the DTCs. These codes are numeric and will tell you what the problem is (e.g., P0171 - System Too Lean Bank 1).
* Auto Parts Store: Many auto parts stores will read the codes for free. Take your car to one and they'll plug in their scanner.
* Mechanic: A mechanic will definitely be able to diagnose the problem.
2. Address the Problem: Once you have the DTC, you can research what it means (there are many online resources) or take it to a mechanic. The cause could be anything from a loose gas cap (a common and easily fixable issue) to a more serious problem requiring repairs. Fixing the problem is the only way to reliably turn off the SES light.
3. Clear the Code (After Repair): *Only after* you've fixed the problem that triggered the SES light, you can clear the code. This is usually done through the OBD-II scanner. Many scanners have a "clear codes" function. After clearing the codes, drive the car for a while to ensure the problem is resolved. If the light comes back on, the problem wasn't fixed.
Important Note: Simply disconnecting the battery or using a "code clearer" tool *without* fixing the underlying issue will only temporarily turn off the light. The light will reappear as soon as the problem is detected again. This is a dangerous practice, as it can mask a serious problem that could damage your engine or compromise your safety.
