Resetting the Check Engine Light: When It’s Helpful and When It’s Risky for Your Car

Few things unsettle drivers more than seeing the Check Engine light illuminate on the dashboard. The immediate thought is often a costly engine repair. But the warning doesn’t always point to something serious. Sometimes the issue is surprisingly simple—bad fuel from a questionable gas station or a little moisture getting into a sensor.

In such cases, many experienced drivers turn to a quick fix: resetting the car’s engine control unit (ECU). The easiest way to do this is by disconnecting the battery. Shut off the car, pop the hood, and remove the negative terminal from the battery. After waiting 10–15 minutes, reconnect it and try restarting the engine. In many instances, this will clear the light.

However, here’s the catch: a reset is not a repair. It only erases the error code stored in the ECU’s memory. If the issue was just a one-off sensor glitch, the light may stay off. But if there’s a real fault in the system, the warning will inevitably return—sometimes within just a few miles.

There’s another drawback. By manually clearing error codes, you wipe valuable diagnostic data. These codes act like a car’s “medical history,” helping mechanics quickly pinpoint the source of a problem. Without them, the diagnosis may take longer and cost more—like erasing fingerprints that could have led investigators to the culprit.

Apart from disconnecting the battery, there are other ways to reset the system. For example, some owners pull the fuse that powers the ECU, following guidance in the vehicle’s manual. The result is the same. The most proper method, however, is using a diagnostic scanner. Basic scanners are easy to buy at auto parts stores, but using them without proper knowledge can do more harm than good—so professionals recommend leaving this step to trained technicians.

Most auto repair experts agree: resetting error codes can be useful in certain situations, especially after a random electronic hiccup. But it’s no cure-all. It won’t fix worn-out parts or serious mechanical issues. If the light comes back after a reset—or if you’re not confident in what you’re doing—don’t take chances. Head to a service shop. Trying to save a few bucks on diagnostics could end up costing much more in repairs.