How to Disconnect Your Battery to Turn Off the Check Engine Light


1. Obtain a code scanner by purchasing one at a local auto parts store, or put down a deposit for a loner. They look like small, hand-held gauges with a screen and usually have two buttons. Place the vehicle in park or neutral with the emergency brake set. Leave the battery cables connected for testing purposes. Open the driver's side door, and look under the dashboard on the left side of the vehicle. You will find a diagnostic connector jack. Plug a code-scanner tool into the connector jack, and start the engine.
2. Look at the small screen on the code-scanning tool. Some code numbers will appear, and they might look very cryptic. The code numbers apply to a certain system-management system that has failed or needs attention. There might be a list of several numbers in a row. Write down each code number exactly as it appears on the scanner tool. You will need to know these reference code numbers for future maintenance procedures, especially if the codes indicate an emission-control system that must be fixed in order to pass a smog test.
3. Once you have the codes written down, you can look them up in a trouble book that comes with the scanner tool, or can be purchased separately. It will define the exact part that needs attention, adjustment or repair. Find the code number and the specific part that relates to it. Write it down. Now look at the buttons on the code scanning tool. One will say 'Erase.' Hit that button to erase all the codes, clearing the vehicle's computer. Shut the engine off and wait for several minutes. Start the engine. The 'Check Engine' or 'Service Engine Soon' light will have disappeared.
4. Place the vehicle in park or neutral with the emergency brake set. Raise the hood. If you wish to turn off the 'Check Engine' or 'Service Engine Soon' light without the aid of a scanner tool, you will use a socket and wrench to disconnect the positive (red) cable on the battery. You must wait at least 15 minutes before you reconnect the positive (red) battery cable with a socket and wrench. Start the engine. The 'Check Engine' light should be absent. Note: with this method, you will not know what systems have malfunctioned to trip the warning lights. However, by using this method, you can turn the warning lights off again should they reappear.