If the check engine light was already on *before* the oil change, the oil change had nothing to do with it. You need to determine *why* the light is on.
Here's what you should do:
1. Get the Diagnostic Trouble Code (DTC): You'll need a code reader (OBDII scanner) to retrieve the trouble code(s) stored by the car's computer. Auto parts stores often have loaner scanners or can read the codes for you. The code will tell you what the problem is.
2. Address the Problem: Once you know the DTC, you can troubleshoot and fix the underlying issue. This might require professional help from a mechanic, depending on the complexity of the problem.
3. Clear the Code (After Repair): *Only after you've fixed the problem that caused the check engine light to come on*, you can clear the code using the code reader. Many code readers have a "clear codes" function. The light should stay off if the problem has been resolved.
Simply disconnecting the battery for a short time will sometimes clear the code, but this doesn't solve the underlying problem and is not recommended. The light will likely come back on if the root cause hasn't been addressed.
In short: Don't try to reset the check engine light unless you know *why* it's on and have fixed the problem. Ignoring it could lead to more serious issues.
