trouble with clt input

[bigwheels6]

Hello,
I'm assembling my first kit, MS2 on a V3.0 board, following the Megamanual instructions. I'm at step 55 and have found a problem. I've built the board with the recommended R7 and R8 values as I am going to run on a GM LT1 engine. I am using a V2.21 stim and a 12v wall wart power supply. When I get connected to Tunerstudio, I have proper function with all of the pot adjustments with the exception of coolant temp (clt). I've checked the stim output for the clt pot on pins 21 to 7 and the resistance tracks with movement of the knob. I've checked pin 25 on the CPU and its solid at 4.95V. I've verified correct values for R7 and R8 as well as checked accross C6 and C7 and found resistance in the Mohm level. I tried to remove a leg from C6 and C7, but I don't have solder removal tools here and went with the measured resistance. I've noticed that if I touch my finger to the back of the board where the bank of input resistors and capacators are connected, letting my finger short accross them, the coolant gauge on Tunerstudio will flicker, but never settle on a value. There aren't any appearant solder bridges, and I can't find any questionable looking solder connections on the CPU socket or the input section.
I'm feeling a bit stuck.
Not sure what to try next.
Anybody have suggestions?

[trakkies]

It sounds like there is no ground connection between MS and the CTS pot on the stim. That would account for the 5 volts at the processor and it not changing with the pot.

[bigwheels6]

I shorted pins 21 and 7 on the stim while it was connected to tunerstudio and there was no change in clt. If I did the same short between 20 and 7, IAT responds on the screen.
I'm wondering now how to verify the trace between pin 21 and other points in the input section. Not sure where to probe at this point.

[trakkies]

With MS not powered, check continuity between pin 21 and the junction of R7, C6, R8. On the stim, check continuity between the ground side of the CTS pot and pin7 You could also check the CTS pot itself.

[bigwheels6]

The open was right next to the MAP solder points. I ran a wire from the back of the board at the DB37 solder point through an available gap to the right hand side of R7. I was guilty of using a worn soldering iron tip when I connected the MAP. A drop of solder fell on the board and when I removed it, I inadvertently cut the trace connecting pin 21 to the input section. 
Thanks a bunch for the help!