Follow our guide to learn how to reset your check engine light without needing a trip to the mechanic or dealership. It might be easier than you think!
Seeing the dreaded check engine light on your dash can be a worrisome experience. The check engine light will turn on in your car to tell you something is wrong. But unless you know what is triggering your trouble codes, it can be difficult to identify the problem. In this article, we’ll go over what your car may be trying to tell you, and how to turn off that pesky light on your dash.
Why Is My Car’s Check Engine Light On?
Your car is a complicated piece of machinery, full of different systems designed to operate within specified parameters. If one of those systems begins malfunctioning, a sensor will usually send a signal to the engine’s computer to trip the check engine light. If your check engine light (CEL) is on, it’s best to immediately address the issue to avoid compounding the problem.
Some common reasons for a car’s check engine light coming on include:
- Loose gas cap
- Negative battery cable
- Faulty spark plugs
- Malfunctioning oxygen sensors
- Internal problems with the engine
How Do I Know What’s Wrong with My Car?
If your vehicle is a 1996 model or newer, then deciphering a check engine light code is surprisingly easy. You will need a tool called an OBD II (onboard diagnostics version 2) code reader, which plugs into a diagnostic port (usually located under the dashboard). This scanner tool will provide a code readout that you can use to diagnose the problem.
For those who want a more compact design that remains plugged in (vs. the traditional corded code readers), there are also Bluetooth code readers designed to work with your smartphone.
Don’t worry if you don’t own a code reader, as many auto parts stores will provide the service free of charge.
How to Diagnose the Check Engine Light
1. Locate the diagnostic port
With your vehicle parked and your engine off, begin by locating the diagnostic port. Automakers usually place them under the dashboard near the pedals, but each car is different. The port should be trapezoidal in shape (matching the connector on your scanner tool). Sometimes you may have to remove a plastic cover to expose the diagnostic port.
2. Retrieve the code
With your scanner tool handy, start the engine and proceed to plug the scanner tool into the diagnostic port. The scanner tool should illuminate and generate a code after several seconds. Once the code appears on the display, write it down. It should read in the format of P1234. Proceed to shut off the engine.
3. Diagnose the fault code
Using the internet or a code list provided with your scanner tool, you will be able to identify which system has malfunctioned. Some codes are very specific (such as a failed ignition coil pack on cylinder 4), while others are more generalized (such as an evaporative system leak). If the check engine light code is still unclear, resources such as online discussion boards or a mechanic may be able to provide a clearer answer.
How to Reset a Check Engine Light
For best results, you are encouraged to make any necessary repairs, or confirm that the component in question is functioning properly.
1. Connect the OBD II (OBD2) scanner
Start by connecting the OBD II scanner to the vehicle’s diagnostic port. The OBD II port location varies by vehicle, so refer to your vehicle’s manual. Proceed to start the engine and let the code reader display the check engine light codes.
2. Erase the fault codes
Using the code reader’s user interface, proceed to erase the logged check engine codes. Once you are done, no error codes should appear. You may turn the car off at this point.
3. Clock some miles
To make sure the check engine light does not reappear, it’s recommended that you drive your car 30 to 100 miles. This enables the vehicle’s “Drive Cycle” to reset, as the various sensors need time to recalibrate.
If you plan to do an emissions test, the check engine light must remain off, and the “drive cycle” must register as ready. Typically 50-100 miles of driving will take care of drive cycle readiness, but it’s best to check with your dealership or mechanic concerning your specific vehicle application.
Alternative Methods for Resetting a Check Engine Light
While a code reader is usually the most immediate way of resetting a check engine light, there are a few alternative methods you could try:
- Temporarily disconnect the battery; start by locating the negative terminal and disconnecting it, then repeat with the positive terminal
- When reconnecting the battery, start by connecting the positive terminal, and then reconnect the negative cable
- Turn the car ignition off, then restart the car
- Continue driving and let the light go off on its own (only suggested if you have made the necessary repairs without erasing the fault code)
My Pre-1996 Car Has a Check Engine Light
If you have a check engine light and your car is older than 1996, then diagnosing the cause requires a bit of a different process. While each vehicle is different, codes are displayed via a sequence of CEL flashes (not unlike Morse Code). The number of light flashes corresponds to a fault code.
Resetting the check engine light on a pre-1996 vehicle is performed by making the necessary repairs. If the CEL remains illuminated, then temporarily disconnecting the battery may be necessary to reset the light.
What if my check engine light reappeared?
If your check engine light reappears, then additional repairs may be necessary. If you’re not comfortable with automotive troubleshooting, it’s advisable to seek the assistance of a professional mechanic.
Checkmate to the Check Engine Light
Next time a check engine light finds its way to your dashboard, you’ll be ready to diagnose and reset it just like a pro.
Disclaimer: This article is not intended to be a substitute for professional advice and is for information only. Always seek the advice of a certified professional or your vehicle manufacturer. If attempting any repairs yourself, take all safety precautions as necessary.
