Trans. Q. on Dreaded '01 S80: Faulty ABS Module? (W/ CODES)

[DanSC]

I have been planning to buy my friend's 2001 S80 2.9 largely because it's already had the transmission changed. The car has 115,000 miles and the transmission was changed on warranty by the dealer at 80,000 miles. But about a week before I was to buy it, the Transmission Service light came on and the car went into Limp Home mode. She took it to her independent Volvo specialist, who said the problem was not the transmission, but a faulty ABS module. The module was replaced and the codes were cleared, but the light came on again and the car went into Limp Home mode.

The mechanic has found a code relating to shift solenoid 1 (I don't know the exact code, I will try to find out today), but says the transmission shifts fine and that he can hear the solenoid moving in the transmission. He thinks the computer either isn't receiving or doesn't recognize the signal that the car has shifted and assumes the worst, putting the car into Limp Home mode.

The mechanic would like to take out the transmission and look for faults inside it, with replacing the transmission as an option.

In my very limited research, I found something that says the transmission speaks to the main computer though the ABS module. Could the ABS module still be the problem? I know these transmissions aren't the most reliable, but just need a car for a year or two and I can't imagine the transmission went bad after only 35,000 miles.

[DanSC]

I got in touch with the mechanic. He runs a great shop, but it's just him and a few other people, so I can't always get him on the phone.

He told me the S80 was producing the following trouble codes.

ECM-530D: Diagnostic trouble code (DTC) in another control module
TCM-0002 Gear shift solenoid S1. Signal missing

Considering the transmission only has 35,000 miles on it, this is making me think it wasn't just the ABS module that was bad, or maybe the ABS module was fine and another one is bad.

Other than the transmission module, what other modules would cause these codes? Keep in mind that the car does run, the transmission shifts, and the transmission solenoids seem to be working (he says he can hear it), but the car will still show the "Service Transmission" light and go into Limp Home mode.