How do you reset ecu for Nissan Sentra gx 2003?

To reset the ECU of a 2003 Nissan Sentra GX, disconnect the negative battery terminal and wait for about 10-15 minutes to allow the system to reset. After that, reconnect the battery terminal. Start the vehicle and allow it to idle for a few minutes, which helps the ECU recalibrate. If you have any persistent issues, consider using an OBD-II scanner to clear any stored trouble codes.