Could be an MC18 or MC28 bottom-end - neither of those have a GPS, but both have a TPS.
The GPS is just a 6 position switch that earths (grounds) the wire corresponding to the gear you are in. If you cannot retro-fit an GPS for any reason, I suggest grounding the 3rd gear wire so the PGM "thinks" it's in 3rd gear all the time!
There is an MC21 wiring diagram for you to follow in the Workshop section.
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Andy.
NSR-WORLD.COM
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