if it is a k21-k25 engine (platinum 1 series) then the info may be the same as in the Catibishi or Mitsupillar and their info says;
The instrument panel shows error code E31 in the hour meter display area.
The throttle control motor relay is either locked ON e.g. relay tips are welded or the relay is locked OFF
e.g. an open circuit too or from the relay.
Test the EGI 1, EGI 2, and ETC relays for proper operation. The relays are located in the blue relay box.
Check for continuity between throttle control terminals #3 and #6.