Disconnecting the battery can turn off the check engine light, but the computer must relearn its operating parameters and driveability may be affected until then. If the original fault remains, the light will return, so diagnose the cause rather than only clearing the light.
The owner of a 2003 Audi A4 asked whether disconnecting the battery resets the computer and turns off the check engine light. The expert said it will extinguish the light, but the computer must relearn its parameters, driveability may be affected until then, and the light will return if the original condition still exists.
