The check engine light (or service light) normally comes on when there is a problem with your vehicle's emission control system or other computer controlled system. The light generates a code that can help you determine the problem so you can have it fixed. You may also need to manually reset the light after making repairs if the code does not clear automatically. The best way to reset a check engine light is to use a code scanner. However, if your vehicle was built before 1996, you can simply disconnect the battery to reset it.
Method 1 of 2: Use a Code Scanner
Step 1. Purchase or borrow an OBD-II code scanner
"OBD" stands for "On Board Diagnostics" and OBD-II scanners are appropriate for all vehicles made after 1996. Purchasing a code scanner can be expensive, so it is best to borrow one. unless you plan to use it frequently. Some auto parts stores loan scanners to customers, or you could borrow one from a friend or family member.
Please note that vehicles made before 1990 may not have an OBD port under the dash. If they do, it may be an OBD-I port instead of an OBD-II port, so you may need a different scanner
Step 2. Connect the scanner to the port underneath the steering column
Modern vehicles have ports specifically designed for OBD scanners. Look under the steering column to find the port and then connect the cable that is attached to the scanner to the port. Check your vehicle's manual if you can't find the port.
Step 3. Turn the key to the "on" position and press the "read" button on the scanner
Put the key in the ignition and put the vehicle in "on". Do not start the vehicle. Once the dash lights come on, turn off all vehicle accessories, such as the radio. Then, press the "read" button on the scanner to access the code for the "check engine" light.
- The code will be a series of letters and numbers. Record all the codes so you can find out what they represent and make the necessary repairs to your vehicle.
- Some scanners will define or explain the codes while others will not. If you don't see a definition, look up the code in the user manual or online.
Step 4. Press the "erase / clear" button on the scanner and then turn off the key and unplug it
Clearing any codes present will turn off the check engine light temporarily. After pressing "erase / clear" and waiting until you see the message "no codes", you can turn off the vehicle and unplug the scanner. However, clearing the codes does not fix the problem. If the check engine light comes on, it is best to take the vehicle to a mechanic for professional diagnosis and repair.
once the OBD system resets (which occurs after a few drive cycles or a certain number of miles, depending on the vehicle), the light will come back on if the problem has not been fixed.
Method 2 of 2: Disconnect the Battery
Step 1. Remove the negative cable from the vehicle's battery
Open the hood and locate the battery. Use a wrench to remove the negative wire, which is usually covered with a black plug and marked with a minus sign, from the terminal.
Clearing codes by disconnecting the vehicle's battery can also clear the memory of the radio and other on-board components.
Step 2. Drain the remaining electricity from the capacitor
Hold the horn for 30 seconds or try turning on the vehicle's lights. Neither the horn nor the lights will work as there is no power reaching them, but trying to do so will consume the electricity in the capacitor.
Step 3. Wait 15 minutes and reconnect the battery
Leaving the battery disconnected for about 15 minutes will ensure that the vehicle's systems are fully reset when you reconnect the battery. Secure the negative cable back to the terminal and cover it with the plug (if applicable). Disconnecting the battery will clear the error codes and reset the check engine light.
- Reputable auto shops will not reset the check engine light without fixing the problem that caused the light to come on.
- Consult a mechanic or workshop if you need help resetting the check engine light or deciphering error codes.
- Your vehicle's emissions monitors will record the reset, so you won't pass the emissions test if you drive a car immediately after resetting the codes. Drive the car at least 320 km (200 miles) before taking it for an emissions test.
- Be careful when disconnecting and reconnecting the battery.