Determining if the Check Engine Light Was Erased or Cleared

Have you ever wondered if there is a way to know if a seller cleared the check engine light on a car? Or maybe the mechanic cleared the check engine light without fixing the problem? This article will show you how to use an OBD2 scanner to determine if the check engine light was recently reset.

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The check engine light (CEL) is an important indicator of potential problems with your vehicle’s engine or emission control system. If the light is illuminated, it is important to have your vehicle inspected as soon as possible. However, in some cases, a mechanic may erase the CEL to clear the code and turn off the light, making it difficult to know if the problem has been resolved. To determine if the check engine light has been erased, there are a few ways you can check. One method is to retrieve the vehicle’s diagnostic trouble codes (DTCs) using an OBD-II scan tool. Another way is to pay attention to the CEL cycle – the light should illuminate briefly when the ignition is turned on, then turn off if there are no codes stored in the system. If the light stays on after the initial cycle, it indicates the presence of a trouble code.

How do people reset the check engine light?

First, it is important to understand how the check engine light is reset. Check engine light can be reset by clearing the codes with an OBD2 scanner or disconnecting the battery. Both methods temporarily clear all the Diagnostic Trouble Codes (DTCs) from the On-Board Diangntoic computer. This procedure also reset the various systems in the car to the Not Ready state.  Depending on the problem, the check engine light could come back immediately or take up to two weeks to turn on.

You can not pass a state emissions test by clearing the codes this way.

How to tell if the Check Engine Light was reset

To find out if the check engine light was reset, you will need an OBD2 code reader. The UCAN-I Scanner can read check engine lights, and the YOUCANIC Full System Scanner is a professional scanner that can run through all the control modules of your vehicle

Make sure the scanner you buy can display I/M Monitor Readiness Status; the YOUCANIC Full System Scanner can show your vehicle’s emission readiness status and every control module on your vehicle.

1. Turn the key to the ON position. Do not start the car.
2. Locate the OBD-II port under the dashboard and plug in the OBD2 scanner.
3. The scanner should power on once connected to the OBDII port. Press Read or Enter on the scanner, depending on your scanner model.
4. Please scroll down to the I/M Readiness menu and select it.
5. Look at all the systems. If most say NOT READY, the check engine light was recently reset. They will say one of the following.
   • Ready / OK- On-Board Diagnostic has completed monitoring this system and passed the test.
   • Not Ready / Pending – This system’s monitoring is not yet completed. You need to continue driving the vehicle.
   • Fail – OBDII monitored this system, but it failed to pass. Typically a Diagnostic Trouble Code (DTC) is set, and the check engine light has or will turn on soon.

• A car that has not had the ECU codes reset will have all the systems as Completed / Pass / OK and maybe a few Not Applicable if certain systems are not installed.

• If the codes were recently reset, you would notice that several emissions monitoring systems will show as Completed while others will be Not Ready or Pending (or maybe even Fail).

We hope you find the How To Find Out If Check Engine Light Was Erased by Seller guide helpful. Check these troubleshooting and repair guides for more help on your vehicle.

Can a mechanic reset the check engine light, and clear codes without fixing the problem?

To know if a mechanic cleared the check engine light without fixing the problem, you can do the following:

1. Check the vehicle’s maintenance records: The mechanic should have documented the check engine light issue and any repairs they made in the vehicle’s maintenance records.
2. Monitor the check engine light: If the problem wasn’t fixed, the check engine light is likely to turn back on. Keep an eye on it and see if it illuminates again.
3. Retrieve the trouble codes: You can use an OBD-II scan tool to retrieve the vehicle’s diagnostic trouble codes. This will give you a clear picture of what the problem is and whether it was fixed or not.
4. Test drive the vehicle: Take the vehicle for a test drive and pay attention to any symptoms or warning signs that the problem still exists, such as rough idling, reduced power, or unusual noises.
5. Get a second opinion: If you’re still unsure if the problem was fixed, you can take your vehicle to a different mechanic for a second opinion. They will be able to diagnose the issue and confirm whether the check engine light was erased without fixing the problem.

If the mechanic did clear the check engine light without fixing the problem, it’s important to address the issue promptly to prevent further damage to the vehicle.

Frequently Asked Questions