I purchased an '85 Fiero 2M4 with an SC SII 3800 swapped into it mated with the 4T65E-HD from a '99 Grand Prix GTP. It had a digital dash in it that didn't work very well so I decided to swap back in a stock dash. I found one on Ebay from an '87 4cyl Fiero. Everything seems to work. Right now I'm tackling the speedometer buffer circuit that is lined out here: http://www.gmtuners.com/fiero/fmods.htm As far as I know I've done everything correctly, but my speedometer isn't reading. I believe I have all of the correct components, the diode in the correct direction, the GTP harness' wires are coming from the correct places, and everything looks good according to the multimeter. The speedometer gets 12V, but continues to read 0 while driving. The PCM has the high (yellow) and low (purple) inputs from the PCM going into the correct pins (65 and 64). I have the buffer circuit getting input from the dark green wire (pin 55) coming from the PCM, and outputting into the high wire (yellow) of the Fiero's dash (can't remember which pin that is). If anyone else has had any trouble with this buffer circuit and figured it out, I'd really appreciate some help.
Edit: After doing some more research. I found someone with the exact same issue as me. His problem was that the PCM was tuned by ZZP, and they turned VATS back on (supposedly it's turned off on stock GTPs). I have a pretty good feeling that the original owner of my vehicle had his PCM tuned by ZZP since he installed several aftermarket ZZP parts and put a ZZPerformance sticker in my rear window... I contacted a local tune shop to see if they could turn it on for me. They said that ZZP locks their software after tuning so I have to contact them. I called them and got sent to voicemail after being put on hold. I explained my issue and gave them my info but I doubt they'll contact me. I'm planning on contacting them again with a more "I want a tune" message so they'll think about the money. Has anyone here had any dealings with ZZP? I'd like to know how difficult it will be to get this issue fixed.
Thanks in advance!
[This message has been edited by Crazy_ones24 (edited 05-21-2023).]
