OK I took the car to the mechanic since I couldn't figure out wtf was wrong (got codes 15 and 21, replaced TPS and temp sensor, still get codes and bad TPS symptoms). He called and said it needed a new battery.

Put in a new battery, strarted it up, and went for a 20 minute test drive. Half way through the check engine light came on! Same 2 codes. The light turned off after a few seconds though (before it was on all the time) and the car was running normally again.

I took the car back and explained what happened. His best guess was bad ground or bad wiring between the computer and the two sensors. The smaller wire coming off the negative battery terminal wasn't really grounded, as I found it was attached to a PILE of rust that used to be the wall next to the battery.

Any ideas? Anyone ever made an entireley new duke wiring harness? Need my car running again...

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1984 Fiero SE

UPDATE: Fixed the bad ground, went to start the car, and just got a "cra cra cra cra cra cra..." the few times I tried. Then I went back to the engine compartment and wiggled the wiring harness that sits on top of the transmission, climbed back in and turned the key, and it fired right up. Checked the check engine code it had set, and it was just code 21.

Anyone? Can I just rewire that sensor somehow? Anyone have the wiring diagram that shows how it's plugged into the computer?

It could be worse, maybe there is a 'bad' spot in the harness where the wires are broken, rotted, cracked, melting/melted,etc..

I would pull the loom off that section of wires and check them all. The other wires may be damaged too, but only that certain one is bad enough to show signs. Preventative maintence ya know... I had that same issue blowing the hell out of starter relays. Completely ruined them, I pulled the harness apart and I found this..

https://www.fiero.nl/forum/Archives/Archive-000001/HTML/20050410-2-056963.html