How to Reset a Check Engine Light and Clear Error Codes

How To Reset A Check Engine Light And Clear Error Codes

A glowing check engine light is never a welcome sight. This amber indicator on your dashboard signals that your vehicle’s on-board diagnostics system (OBD) has detected a problem with one of your car’s systems.

The check engine light can give you fair warning of an impending issue, allowing you to get repairs before major damage occurs. However, it can also trigger unnecessarily, leaving drivers frustrated and confused about what to do next.

Fortunately, you can reset a check engine light on your own without any fancy tools or computer scanners. This straightforward guide will teach you four methods for turning off a check engine light and potentially saving yourself a trip to the auto shop.

With a few basic steps, you can reset the light and clear any codes to find out if the problem was minor or continues to persist. Read on to learn how to get rid of that annoying check engine light and get back to normal operation.

How Vehicle Computers Work

The vehicle’s ECU (engine control unit) is an onboard computer that monitors sensors throughout critical systems like the engine, transmission, and emissions. It oversees functions like fuel mixture, ignition timing, valve operation, etc. to optimize performance.

When a sensor detects something outside normal parameters, it alerts the ECU. The ECU then turns on the check engine light to notify the driver of the issue. It also generates fault codes pointing to the specific sensor or system causing the problem.

How Vehicle Computers Work
How Vehicle Computers Work

Why Does the Check Engine Light Come On?

The check engine light alerts drivers to problems detected by the vehicle’s onboard diagnostics (OBD) computer. Sensors monitor everything from oxygen levels to ignition timing and emissions controls. When one of these sensors detects an issue, it triggers the check engine light to switch on.

Common causes include faulty oxygen sensors, ignition problems like bad spark plugs, mass airflow sensor failures, computer glitches, loose gas cap allowing fuel vapor escape, and catalytic converter damage. Any issue that impacts engine performance,

emissions controls, or sensor readings can cause the OBD computer to turn on the warning light. Diagnosing the specific diagnostic trouble code can help identify the exact problem. But generally, the check engine light means a sensor detected an abnormality needing attention.

Why Does the Check Engine Light Come On?

When to Reset the Check Engine Light

Before resetting the check engine light, it’s smart to understand what caused it to turn on and if the problem has been fixed. If faulty components triggered the light, it will simply turn on again after reset until you complete repairs.

However, there ARE appropriate times when homeowners can and should conduct a DIY check engine light reset. This includes:

  • After Ignoring It: Let’s say you properly diagnosed the issue but put off repairs. Resetting clears the previous code so you have a clean slate moving forward.
  • Loose Gas Cap: As mentioned, a loose fuel cap often triggers the OBD sensor. Tightening or replacing the cap fixes this.
  • Repairs Complete: Once you or your mechanic replaces a faulty part, resetting turns off the warning light.
  • Battery Disconnection: A battery disconnect to switch out cables or electrical work requires a computer reset to function properly.

Unless the above conditions are met, it’s best to have your vehicle serviced before DIY resets. Technicians have the high-tech tools to accurately diagnose OBD codes and determine if resets are appropriate. Let’s review the common reset procedures they perform.

When To Reset The Check Engine Light
When to Reset the Check Engine Light

How to Reset a Check Engine Light

Using an OBD-II Diagnostic Scanner

The most precise way to reset a check engine light is with an OBD-II diagnostic scanner. Technicians and advanced DIYers use these high-tech scanners to read, diagnose, and erase check engine codes. They plug into your OBD port and connect to the vehicle’s computer system. From there, users can view stored codes, freeze frame data, perform tests, and safely reset the check engine light.

Here is a step-by-step process for resetting with an OBD scanner:

  • Locate the Data Link Connector (DLC) port under the dash, driver side. This is where your scanner plugs in. Connect the scanner and turn on the ignition (not the engine).
  • Use the scanner to access stored codes. Write down or take screenshots of any codes.
  • Follow scanner prompts to reset check engine light and clear DTC codes. Turn off ignition and disconnect scanner. Start engine to verify light is off.

Using a scanner provides proof you fixed the true issues instead of just hiding them. The codes will repopulate and light will turn back on if faulty parts remain.

Using An Obd-Ii Diagnostic Scanner
Using an OBD-II Diagnostic Scanner

Disconnecting the Battery

A more rudimentary way DIYers can reset a check engine light is by disconnecting the battery. This erases all computer system data, including diagnostic codes, and forces a restart. When the battery reconnects, everything in the ECU resets including the check engine light.

Here are the steps for battery reset:

  1. Turn off ignition and remove key.
  2. Disconnect the negative battery cable (black wire).
  3. Wait 15-20 minutes to discharge power.
  4. Reconnect the battery cable.
  5. Start engine. Check engine light should remain off.

This crude reset method may work temporarily but also clears radio stations, clock settings, and other electronics. It works best after repairs are complete and battery service is also needed. The light will illuminate again if underlying issues go unresolved.

Disconnecting The Battery
Disconnecting the Battery

Turning Ignition On and Off

For newer cars that are fully computerized, owners can use a sequence of ignition switches to reset the check engine light. This forces a restart and recalibration of the ECU system. It works best for minor errors versus major mechanical issues.

Follow these steps to do the ignition switch reset procedure:

  • Insert key into ignition and turn to the ON position. Do not start engine. Wait for 3-5 seconds until dash lights illuminate.
  • Turn ignition OFF and remove key. Repeat the process 4-5 times until check engine light blinks or shuts off.
  • Start vehicle and verify the light stays off.

This resets the computer system in a similar way to disconnecting the battery. It saves you from needing to access the battery, but the light will still return if repairs are needed.

Turning Ignition On And Off
Turning Ignition On and Off

Wait It Out

Lastly, just driving as normal for 50-100 miles may be enough to reset your check engine light. This works by allowing the OBD computer to complete its full cycle. Driving clears any pending codes or temporary glitches that switched on the light.

Simply operate your vehicle gently as usual. Avoid aggressive acceleration and braking. The check engine light should switch off within a couple days of normal driving. Of course, this wait-it-out method only works if the problem resolved itself and no repairs or resets are necessary.

When to Seek Professional Help

While the above DIY methods can reset your check engine light, only a professional scan and repair can tell if issues have been properly fixed. Seek help from a certified mechanic, dealership, or auto shop if:

  • The light turns back on immediately after resets.
  • You have significant performance issues like misfires, stalling, or loss of power.
  • Multiple reset attempts fail to turn the light off.
  • The check engine light is flashing or blinking.

Flashing means an urgent issue exists, like catalyst damage. In these cases, continuing to drive risks further damage. Shut off the vehicle and tow it to the nearest shop for diagnostics right away.

For minor issues, DIY resets may be suitable following repairs. However, anything complex or that reoccurs despite your best efforts requires professional scanning. Resetting a check engine light without fixing underlying problems just causes more trouble down the road.

When To Seek Professional Help
When to Seek Professional Help

common symptoms that may trigger the check engine light:

A variety of performance, operational, and sensory issues can indicate engine troubles that activate the check engine warning light. For example, an underpowered feeling when accelerating, rough idling with engine shaking or RPM fluctuations,

and hard starting due to compression issues are all common symptoms tied to check engine light illumination. Drivers may also notice the malfunction indicator light specifically targeting emissions problems turns on in conjunction with check engine activation.

Symptoms like overheating, misfiring cylinders, sputtering or stalling, and burning odors relate to sensor detection of temperature changes, ignition failure, fuel delivery problems and leakage hazard. Even hard to diagnose issues like computer

glitches or wiring faults can manifest through performance symptoms that then trigger the amber check engine glow. Any out of the ordinary sights, sounds, smells or driving characteristics basically means a deeper engine issue is at play. Pay attention if your vehicle exhibits sluggish power.


Can I reset my check engine light myself?

Yes, you can reset the check engine light yourself in some cars by disconnecting the battery for a few minutes. This temporarily erases the codes that triggered the light. However, it’s better to use an OBD2 scanner to read the codes first so you can address the underlying issue. Resetting without a scanner will just cause the light to come back on shortly after.

How do I turn my check engine light off?

The best way to turn off the check engine light is to repair the problem that caused it to turn on in the first place. Use an OBD2 scanner to read the diagnostic trouble codes, then make any repairs to fix the issue. Clearing codes without addressing the root problem will only cause the light to illuminate again soon after. Turning the light off without proper diagnosis and repair is not recommended.

How can I clear my check engine light without a scanner?

You can temporarily clear the check engine light without a scanner by disconnecting your car’s battery for 30 minutes. This erases the codes that turned on the light. But it will come back on after driving a short distance if the underlying condition still exists. Using a scanner to read codes is best before clearing so you can properly diagnose and repair.

Can Autozone clear codes?

Yes, most Autozone locations can plug into your car’s OBD2 port and read any diagnostic trouble codes that triggered the check engine light. They can then clear the codes which will turn the light off. However, without repairing the underlying problem first, the light will just come back on shortly after clearing.

How do I clear my engine error code?

First use an OBD2 scanner tool to read the engine error code and diagnose the issue. Make any necessary repairs to resolve the problem that triggered the code. Once the underlying condition is fixed, you can clear the code by disconnecting the battery for a few minutes, or using a scanner tool to reset the computer and turn off the check engine light.

Does resetting check engine light clear codes?

Yes, resetting the check engine light will clear the diagnostic trouble codes that caused the light to turn on. However, it will not fix the underlying problem. The computer will detect the fault again shortly after and the light will illuminate again with the same code. It’s best to properly diagnose and repair the issue first before resetting.

Can you clear an error code on a car?

Yes, you can clear an error code that triggered the check engine light on your car. OBD2 scanner tools allow you to reset the car’s computer which erases existing codes. However, it’s best to diagnose the code first, make repairs to fix the underlying problem, then clear the code once resolved. Otherwise, the same error will just recur shortly after clearing.

Does disconnecting battery reset codes?

Temporarily, yes – disconnecting the battery for 30 minutes or more will erase any existing diagnostic trouble codes that turned on the check engine light. But it does not fix the underlying problem. The computer will just detect the fault again shortly after and light up the check engine light with the same code if the issue was not properly repaired first.


In summary, a check engine light coming on indicates there is a problem with your vehicle’s emissions system. Diagnosing the issue can be done by connecting an OBD-II scanner tool to read the error codes. For minor issues, simply disconnecting

the battery for 15 minutes can reset the check engine light. However, it’s best to repair the underlying problem first before resetting the light. If the light comes back on, further diagnosis and repair is needed. Clearing error codes without fixing the

root cause will only mask problems and potentially lead to more serious issues down the road. With the right scanner tool and some mechanical skills, resetting a check engine light is usually a straightforward process.

But always have the vehicle properly repaired by a professional technician for safety and compliance with emissions regulations.

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