Here's the proper procedure:
1. Diagnose the Problem: The check engine light itself doesn't tell you *what* is wrong. You need to get a diagnostic trouble code (DTC). This can be done in a few ways:
* OBD-II Scanner: The most reliable method. Buy a relatively inexpensive OBD-II code reader (available at most auto parts stores). Plug it into the OBD-II port (usually under the dashboard) and it will read the trouble code(s). This code will give you a clue about what's causing the light.
* Auto Parts Store: Many auto parts stores will read the code for free. They can then help you determine the likely cause and suggest parts or repairs.
2. Repair the Problem: Once you know the DTC, you can start to troubleshoot and repair the issue causing the check engine light. This might involve replacing a sensor, fixing a leak, or addressing a more complex electrical or mechanical problem. Some repairs are simple DIY projects, while others require professional help.
3. Clear the Code (After Repair): *Only after you've successfully repaired the problem*, you can clear the code. There are a few ways to do this:
* OBD-II Scanner: Most scanners have a "clear codes" function.
* Disconnect the Battery: This is a less reliable method. Disconnect the negative (-) battery terminal for about 10-15 minutes. This will reset the computer, but it won't necessarily clear the underlying problem if it wasn't fixed. Reconnect the battery and start the car. The light may take a few drive cycles to turn off if the issue is truly resolved.
Important Considerations:
* Drive Cycles: After clearing the code (and fixing the problem), you might need to drive the vehicle for several drive cycles (start, warm up, and drive for a while) before the check engine light turns off. The computer needs to verify that the problem has been corrected.
* Return of the Light: If the check engine light returns after clearing it, the problem wasn't properly addressed. You'll need to repeat steps 1 and 2.
In short: Don't just reset the light. Find out what's causing it and fix that. Ignoring the check engine light is risky and could lead to costly repairs down the road.
