Originally Posted by mjt

I dont think you ruled out a bad TCCM. You ruled out the switch and the connection corrosion. So you actually opened up the TCCM and made the measurements at F14 and F16 on the TCCM pc board with the connector plugged in? I havent tackled the vacuum problems yet but I can tell you there are a few vacuum lines by the power steering and ABS that were totally disintegrated on my 99. One of them actually supplies that vacuum switch on the firewall. It tees off and a line runs into the truck. You might take a look at those hoses for your vacuum problem. I bought used TCCMs at the junkyard when I got to about where you are. I ended up buying and returning several TCCMs til I got one that worked. All of them had corrosion at the connector. The TCCMs get wet from the vent you said is not functioning. That vent is located just above the TCCM harness. You can see it thru your glove box.