How to Turn Off the "Check Engine" Light on Your Dashboard in 3 Simple Steps 🚗 1. Open the Hood: Locate the car battery and use a wrench (socket or adjustable) to disconnect the negative cable. The negative terminal is usually marked with a minus (-) sign and may be covered by a protective cap. 2. Drain Residual Electricity: Press and hold the horn for 30 seconds or turn on the headlights to discharge any remaining power in the system. Although neither will function without battery power, this step ensures that the capacitors are completely drained. 3. Wait for 15 Minutes: Leave the battery disconnected for about 15 minutes to allow the vehicle's system to reset. Afterward, reconnect the negative cable to the terminal and secure it with the cap if applicable. Once reconnected, the error codes will be cleared, and the "Check Engine" light should turn off