Without using scan tool MB991502

1. Turn the ignition switch to the "ON" position while holding the auto-cruise control switch in the "SET" (down) position. Then, within one second, more the auto-cruise control switch up to the "RES" position.
2. Check to make sure the "CRUISE" light on the instrument panel is flashing.
3. Put the auto-cruise control switch in the "SET" (down) position.

Depress the brake pedal and hold for five seconds or more. Release the brake pedal, auto-cruise control switch, then turn the ignition switch to the "LOCK" (OFF) position. The DTC(s) are now erased.

Fig 1: Erasing Diagnostic Trouble Code Using Auto-Cruise Control Switch

Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.