How do you reset the ecu in a 92 Mitsubishi diamante?

To reset the ECU in a 1992 Mitsubishi Diamante, disconnect the negative battery terminal and wait for about 10-15 minutes to allow any residual power to drain. After that, reconnect the negative terminal. This process clears the ECU's memory and resets any stored trouble codes. It's also a good idea to drive the vehicle for a short distance to allow the ECU to recalibrate.