fuel gauge issues

OK here are the specifics 97 GT w/ 3800 been running on odometer for fill ups. I replace the sending unit and it does the same thiong as before. unplugged it pegs high plugged in it is pegged low with the low fuel light on.
I'm thinking it might be a bad connection some where reducing voltage from the pcm to the unit. Anyone know what the voltage at the sending unit should be? I tried just grounding the return side of the sending unit and it acts like it is plugged in so the ground seems ok. My cheap POS voltmeter is showing about 8 volts at the purple wire to the sending unit. I have replaced the pcm (for other reasons) and both units had the same thing going on. This is driving me nuts cause it should be simple - pcm sees voltage at sending unit which grounds through a variable resistor thus changing the voltage and the fuel reading.
Does any one have the pcm pin out for a 97 gt?

Just send me a private message with your regular email address and I'll send you a PDF file wiring diagram for 1997.

Thanks, pm sent.

You're welcome. File sent and good luck!

Well I think I narrowed it down to the gauge cluster.
I read somewhere that the 97 inst cluster is not interchangable with the 98-03 years due to the pinout on the plugs in back being different. Any one know for sure?
I found a couple of clusters on line but don't want to plunk down my hard earned cash if it won't work.
If anyone has a source for such things I would appreciate the link.
thanks,
Bob

It depends on what time of the year it was made but the wiring did change. For example certain '97.5 can use a '98 IP cluster but I doubt earlier production '97s can.

Try Ed Morad Parts Company on EBay. He specializes in used Grand Prix and other GM car parts.