My 94 Buick set a code P0640 QDM 1 fault this morning. It only happened once however this could be a sign of a PCM failure coming. Quite a few of these PCM's from that era have quad driver failures once they reach 30 years of age.
Many GM cars from this era used PCM Part # 16183247. Does anyone have one kicking around? I'll be able to diagnose this better if I get a hard code and can check the curcuits quad driver #1 controls (evap purge solenoid and TCC solenoid) however it wouldn't hurt for me to have a spare PCM anyway.
Be crashing into each other in our walkers at the swap meet looking for software, eeproms, modules.
You might look at the PCM repair places. I have used
Flagship one in the past, as well as Maks for a TIPM & ECU for my end of life crisis Chrysler Convertible. I travel with a spare TIPM and PCM. (Remember when a spare tire was good enough?)
I have spare quad drivers on hand as I ordered a bunch and repaired my spare PCM.
If/when you get to that point, reach out, with the P/N. If they're the same, I'll gladly send you one.
When I was still working we had several F-550 trucks. One lost the speedometer. It had a code for the speed sensor circuit and a code for battery power loss. I cleared the codes and the speedometer worked again so I put the truck back in service. Three weeks later there was a repeat with no speedometer and the same two codes. I pinned out the affected circuits and found no problems so I removed the ecm. I called the dealer and the ecm was obsolete! The truck at the time was 12 years old. I sent the ecm to a rebuilder and it was returned with a nice note saying that the ecm was defective but the components were no longer available to repair the circuit board. We did manage to find a used one and it did fix the problem but soon everything is going to be disposable because it wont be able to be repaired.
I had to replace the PCM on my 94 Chevy pickup for the same reason (however it was much worse- the truck was stuck in limp mode-2nd gear). I also had to replace the PROM in the Buick when I first bought it as it was setting a knock sensor code continuously and retarding the timing. Robert- are you saying you'd need the PN of the quad driver? Not sure how I'd identify the failing one in the PCM.
the TCM in my 02 Duramax went out. It had a short in it blowing the fuse. Bought a used replacement and the truck is back up and running. I have a check engine light on now the the D does not light up. dealer wants $160 to reprogram so truck and TCM match. Glad i did not take this truck to the Ohio show. it would have been a nightmare
in the past, as well as Maks 
for a TIPM & ECU for my end of life crisis Chrysler Convertible. I travel with a spare TIPM and PCM. (Remember when a spare tire was good enough?)