- Pending codes: Some diagnostic trouble codes (DTCs) can remain in a pending state even after the battery has been disconnected. These codes can trigger the check engine light to illuminate until the vehicle's computer runs additional tests and determines whether the problem is still present.
- Persistent issues: If the underlying issue that caused the check engine light to illuminate in the first place is still present, it will likely set the code again, causing the light to come back on after the battery is reconnected.
- New issues: It's possible that a new problem has occurred that is separate from the original issue causing the check engine light. This could trigger a different code and keep the light on.
- Computer resets: Disconnecting the battery can reset the computer's learned parameters and adaptations. While this is sometimes necessary for certain repairs, it can also cause the check engine light to come back on temporarily as the computer relearns and adjusts to the vehicle's operating conditions.
To accurately identify and resolve the issue, you should take the car to a mechanic or auto repair shop for diagnostics using an automotive scan tool. The scan tool can retrieve any stored trouble codes and provide information about the underlying problem.
