Short answer
The light can be reset by clearing the stored codes with an OBD-II scan tool, by repairing the problem and letting the car turn the light off by itself, or, on some vehicles, by disconnecting the battery. The best approach is to read the code and fix the cause first. If the problem is still there, the light will come back.
Find the cause before resetting
Clearing the light also erases stored information that helps diagnose the issue. Read and write down the code before clearing it. If you haven’t done that yet, start with why your check engine light is on and what to do first. Never reset a flashing light just to keep driving; see flashing vs. solid check engine light.
Method 1: OBD-II scanner
This is the method most sources recommend.
- Find the OBD-II port, usually under the dashboard on the driver’s side.
- Plug in the scanner and turn the ignition on without starting the engine.
- Read and record the codes.
- Choose the option to erase or clear codes and confirm.
- Turn the ignition off, restart, and see whether the light stays off.
Many auto parts stores will read codes for free and some will clear them, though policies vary, so ask first. A basic scanner or Bluetooth adapter is also an option for home use.
Method 2: Fix the problem and let it clear
After a proper repair, such as tightening a gas cap or replacing a failed part, the computer re-tests the system. If everything passes over a number of drives, the light often turns off by itself. How long that takes depends on the vehicle and the fault, so there isn’t a fixed answer. Several days of normal driving is not unusual, but don’t rely on that as a rule.
Method 3: Disconnecting the battery
Some sources describe disconnecting the negative battery cable for a period and reconnecting it. This can clear codes on some cars, but it is the least preferred option:
- It may not work on every vehicle.
- It can reset the radio, clock, seat or window settings, and learned engine settings.
- It can cause security or anti-theft prompts on some cars.
- It erases data you could have used for diagnosis.
If you try it, turn the ignition off, follow your manual’s guidance for your car, and disconnect the negative terminal only. If you’re uncomfortable working near the battery, use a scanner instead.
Why resetting just before an emissions test is a bad idea
After codes are cleared, the car’s self-test status is also reset, and it needs time and driving to complete those tests. A test station may not accept a car that hasn’t completed them. Repair first, drive normally, and check your local testing requirements.
How to tell whether a light was recently reset
A scan tool can often show whether self-test (readiness) monitors are incomplete, which can suggest codes were recently cleared. This matters when buying a used car. If the light is off but the monitors are mostly incomplete, ask why.
What if the light comes back
If it returns, the fault is probably still present or the repair wasn’t complete. Get the code read again and compare. If it comes and goes, see check engine light on and off.
FAQ
Can AutoZone clear the check engine light?
Many parts stores will read codes at no charge, and some will clear them, but it varies by location.
How can I reset it on a VW without a scanner?
Battery disconnection is sometimes mentioned, but results vary and it isn’t recommended as a first choice. A scanner is more reliable.
How long does it take to reset on its own?
It depends on the car and the fault. Expect it to take multiple drives.
Is a reset the same as a repair?
No. It only clears the warning.