How Many Miles to Clear a Check Engine Light?
Clearing a check engine light often requires a specific driving distance, depending on the issue and vehicle type. This guide explains the most common requirements and procedures to help you understand what you need to do to clear the check engine light.
Driving Distance Required to Clear a Check Engine Light
Typically, to clear a check engine light, you need to drive your vehicle for a certain number of miles. Most vehicles require you to drive for 50 to 100 miles after the issue that triggered the check engine light has been resolved. This helps the onboard diagnostics system (OBD-II) to complete its self-checks and confirm that the problem has been fixed.
Revised Driving Conditions
It is often recommended to drive under a variety of conditions to ensure that all systems are checked. Drive in city traffic, on highways, and vary your acceleration to cover different drive scenarios. By doing so, you can ensure that all necessary diagnostic checks are performed.
Waiting for the Light to Reset
Following the resolution of the issue, the check engine light should turn off automatically after a certain number of drive cycles. The exact number of drive cycles can vary by vehicle make and model. If the light does not turn off after you have driven enough miles, it may indicate that the problem still persists, and further diagnosis may be needed.
Other Methods to Reset Check Engine Light
Not all issues can be resolved just by driving a certain distance. Some problems, particularly related to the evaporation control (EVAP) system, may require more time or specific conditions. Some EVAP codes can clear after 3-4 days of city and highway driving. Some issues will reset after a few minutes of engine run time.
It is important to note that these methods are contingent on the specific fault and the type of repair that has been performed. A competent repair shop would use a diagnostic scanner to verify the repair after any work has been done. Crappy shops might simply replace a part, disconnect the battery for a few minutes, and take your money before sending you on your way, only to find a new issue on your return visit.
Alternative Methods
Some modern vehicles require an OBD-II scanner to clear the check engine light. For example, removing the negative battery terminal for 3 minutes can sometimes clear the light temporarily, but it will likely trigger it on again due to a permanent defect. For modern vehicles, the check engine light can only be cleared with an OBD-II scanner.
The trick of disconnecting the battery for a decent interval (a few minutes) can sometimes work, but it depends on the type of fault. Historically, the 3-drive cycle method has been used. If the fault has been resolved, the light can reset. However, the exact procedure may vary depending on the manufacturer's implementation of the legislation related to the fault code.
Considerations
Even if you successfully clear the check engine light using these methods, there is likely to be historical data stored in the electronic system. This data can still come back to haunt you during future diagnostic tests, such as a MOT (Vehicle Safety Test) in the UK or emissions tests elsewhere.
I would strongly recommend using a simple and affordable OBD-II code reader to check the issue. These devices can not only clear codes but also give you insights into what is causing the check engine light to illuminate. By understanding the problem, you can address it more effectively and avoid unnecessary visits to the repair shop.