Method 1: Disconnecting the Battery (Clears Codes and Resets Computer)
This is the simplest method, and it clears all stored codes from the PCM (Powertrain Control Module).
1. Disconnect the negative (-) battery terminal first. This is crucial to prevent accidental shorts.
2. Wait at least 30 minutes. This allows the computer's capacitor to fully discharge. Some recommend longer, up to an hour or more.
3. Reconnect the negative (-) terminal.
4. Turn the ignition to the "ON" position (but don't start the engine). Wait a few minutes for the computer to reboot.
5. Start the engine. The check engine light might flash briefly then stay off if the issue causing the codes is resolved. If it stays on or comes back on, the problem persists and needs to be addressed.
Important Note: This method resets *all* learned parameters in the PCM, including things like idle speed and fuel mixture. The computer will relearn these parameters over time as you drive. You may experience slightly rough running for a short period after doing this.
Method 2: Using a Code Reader/Scanner (Clears Codes and Allows Code Viewing)
This is a more advanced method, providing the advantage of seeing what specific trouble codes were stored before clearing them.
1. Obtain an OBD-II code reader/scanner. These are widely available at auto parts stores. Make sure it's compatible with OBD-II vehicles (most scanners from the last 15+ years will be). Some even have the ability to read data in real time.
2. Connect the scanner to the OBD-II port. The OBD-II port is usually located under the dashboard, often near the steering column.
3. Turn the ignition to the "ON" position (but don't start the engine).
4. Follow the scanner's instructions to retrieve and view the diagnostic trouble codes. Write them down! This is crucial for diagnosis.
5. Use the scanner's function to clear the codes. This is typically a simple button press.
6. Start the engine. Again, if the codes return, the problem hasn't been fixed.
Which Method Should You Use?
* Disconnecting the battery is suitable if you just want to clear the check engine light and don't need to know the specific codes. It's simple, quick, and requires no special tools.
* Using a code reader is the preferred method if you want to diagnose the underlying problem. Knowing the codes helps you pinpoint the cause and avoid unnecessary repairs.
Remember, clearing the codes only addresses the symptom (the check engine light). The underlying problem that caused the codes remains and needs to be fixed. If the check engine light comes back on, you should diagnose and repair the problem, not just keep clearing the codes.
