'89 vin C code 21 and 22 and 26

After making several repairs to my recently acquired '89 Electra PA (10 SES codes when I got it), I am still having some issues tracking down problems with the TPS codes 21 and 22 (set ~2 seconds after start-up) and a code 26.

I checked the Cooling fan relays, both measure over 60ohms across their coil, but the fans don't work at all, car has overheated while sitting in drive-through and fan does not turn on when checking SES light. What other devices are controlled by the quad driver on this car? I'm trying to determine if the quad driver has actually failed before I dig too deep into the TPS; but I was hoping that there have been at least a few similar problems that have been solved here on AF. I will try to get back on this evening to check or post anything else I find while I work on it today.

I had an intermittent Code 26 (Quad -Drive Sense Voltage) a few years ago on my 89 PA . I started by checking the simplest things first, which was the electrical connections at the EGR valve, the TCC transmission connector, and the canister purge solenoid connector. I got lucky and my problem was caused by a corroded electrical connection at the canister purge solenoid. I thoroughly cleaned the electrical connector pins and sockets and the Code 26 has never returned.

I hope this helps!