How do you get the check engine light off in a 1991 Nissan Sentra?

To turn off the check engine light in a 1991 Nissan Sentra, you first need to diagnose the underlying issue causing the light to activate. Use an OBD-I scanner to read any trouble codes, then address the specific problem, which may involve replacing faulty components or sensors. After repairs, you can reset the check engine light by disconnecting the negative battery terminal for about 15 minutes or by using the scanner to clear the codes. If the light reappears, further diagnosis may be necessary.