I was just about to buy a friend's 2001 S80 2.9 with the GM transmission, but the Check Transmission light came on and the transmission went into limp home mode (only selects 3rd and 4th). She took it to a independent Volvo specialist shop, but they couldn't find anything wrong with the transmission, but he did find a problem with and replace the ABS module. She went to drive it home from the shop, the light came back on, and the car went into limp-home mode again.

After speaking with the mechanic, he thinks the transmission and its solenoids are working fine, but the computer isn't seeing or recognizing the signal that the transmission has shifted. It then assumes the worst and puts the car in limp home mode. The options the mechanic has given me are to completely replace the transmission or to pull the transmission and try to fix a possible wiring issue inside the case. I should note that the car is on it's second transmission, which only has 35,000 miles.

I haven't found my exact problem in search, but I've seen threads of one malfunctioning module causing problems in other modules. Is it possible that the transmission and its wiring are fine but either the old or new ABS module is leading to a malfunction? If so, how would I diagnose the problem?

 

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, but the car will still show the "Service Transmission" light and go into Limp Home mode.

 

I had a similar issue with my xc90. Except my error code was related or said anti-skid malfunction. Long to short and $&$ later, yes they were deeply related. Hope that helps.