TABLE OF CONTENTS

How to Clear the Codes of a Check Engine Light: A Quick and Easy Guide

When your vehicle’s check engine light (CEL) comes on, it usually means that the engine control unit (ECU) has detected an issue, and it stores a diagnostic trouble code (DTC) to pinpoint the problem. Once the issue is resolved, you might want to clear the stored codes to reset the system and turn off the check engine light. Here’s a simple, step-by-step guide on how to clear the codes of a check engine light.

CEL

What Does Clearing the Codes Do?

Clearing the codes essentially resets the vehicle's onboard diagnostic system (OBD-II) by erasing the stored trouble codes. This turns off the check engine light, assuming the underlying issue has been fixed. It’s important to remember that clearing codes does not fix the problem. The issue must be properly diagnosed and repaired first, otherwise, the check engine light will come back on.

Tools You Need

To clear the codes, you will need an OBD-II scanner (also known as a code reader). These devices connect to your car’s OBD-II port and allow you to read and clear diagnostic trouble codes. Scanners range from basic models that only read and erase codes to more advanced ones that provide live data, perform additional diagnostics, and reset various systems.

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Steps to Clear the Codes

Step 1: Locate the OBD-II Port

The OBD-II port is usually located beneath the dashboard, under the driver’s side, near the steering wheel. It can also be found near the footwell. If you're unsure, consult your vehicle’s owner’s manual for the exact location.

Step 2: Turn Off the Engine

Before using the OBD-II scanner, ensure the engine is off. This helps prevent electrical issues during the connection process.

Step 3: Plug in the OBD-II Scanner

Insert the OBD-II scanner into the OBD-II port. Most scanners will power up automatically when plugged in. If your scanner requires power, turn the ignition to the "ON" position without starting the engine.

Step 4: Turn on the Ignition

Turn the ignition key to the “ON” position, but do not start the car. This allows the OBD-II scanner to communicate with the vehicle’s ECU. The vehicle’s electrical system needs to be powered up for the scanner to retrieve and erase codes.

Step 5: Read the Codes

Once connected, navigate through the scanner’s menu to the “Read Codes” option. The scanner will then retrieve any stored codes from your vehicle’s ECU. These codes can indicate a variety of issues, from engine misfires to exhaust problems.

Step 6: Clear the Codes

After reading the codes and addressing the underlying problem, navigate to the “Erase Codes” or “Clear Codes” option on your OBD-II scanner. Most scanners will ask for confirmation before proceeding. Once confirmed, the scanner will erase the codes from the ECU’s memory.

When the process is complete, the check engine light should turn off. If the light stays on, it means that the issue has not been fully resolved or there is another active fault.

Step 7: Verify the Reset

After clearing the codes, it’s a good idea to drive the vehicle for a short distance (10-15 miles) to ensure the system has reset properly. If the issue is fixed, the check engine light should stay off. If the light comes back on, it indicates that the issue persists or a new problem has occurred.

Additional Tips

● Don’t Clear Codes Before Fixing the Issue: If you haven’t fixed the problem that caused the check engine light, the codes should not be cleared. Clearing codes without addressing the issue will only temporarily turn off the light, but the problem will still be there.

● Use the Right Scanner: For most cars, a basic OBD-II scanner will be sufficient for reading and clearing codes. If you’re dealing with more complex issues, consider investing in a more advanced scanner that offers additional features, such as live data and advanced diagnostics.

● Check Readiness Monitors Before Clearing Codes: If you're preparing for an emissions test, make sure the vehicle's readiness monitors are set before clearing the codes. Some codes may reset the vehicle’s readiness monitors, causing it to fail the test. Driving the car for a few miles after clearing codes will allow the monitors to complete their checks.

● Codes May Return: If you clear the codes and the issue isn’t fully resolved, the check engine light may come back on after some time. This indicates that the problem is still present or there’s another related issue that needs attention.

When Not to Clear the Codes

● Before Emissions Testing: If you’re about to undergo an emissions test, avoid clearing the codes right beforehand. Clearing codes could reset the vehicle’s monitors, causing it to fail the test. Wait until the vehicle is ready, then clear the codes after fixing the issue.

● If the Problem Isn’t Fixed: If you’ve cleared the codes without fixing the problem, the light will likely return. It’s essential to properly diagnose and repair the underlying issue first to ensure long-term vehicle health.

Conclusion

Clearing the codes of a check engine light is a quick and simple task that can be done easily with an OBD-II scanner. However, it’s important to ensure that the underlying issue has been addressed before resetting the system. Clearing the codes without resolving the problem will only turn off the check engine light temporarily, and the light will likely come back on once the system detects the issue again. By following these simple steps, you can clear the codes and get your car back on the road, but always remember to fix the problem first for long-term reliability.

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