Hello all,
This is my first time posting to this forum. I am an electrical repair technician that does free lance work for shops etc. I have a 2001 Volvo S80 T6 that's been quite the undertaking. I'm hoping maybe someone has run into the issue I have and can give me some insight as to where to look.

The symptoms are little to no throttle response, surging idle, A/C inoperative,engine light and the STC warning light is on.

The codes in the PCM that I'm getting are
958F
959F
170D
1300
1600
2000
4020
9530
9540

I'm also getting a few codes in the central module
1A5C
1A55
1A54


The PCM codes popped up stemming from an A/C compressor replacement that the shop did supposedly. My best guess as to what happened is the A/C pressure sensor got shorted to battery voltage somehow because that circuit is shared voltage with other circuits I believe. But that's only a theory as the guy that did the work said he doesn't know what happened lol.


I tried clearing the codes and they come right back. I'm using an OTC Genisys with software revisions that go up to 2005 for European vehicles.

If anyone can help me along I'd really appreciate it. I've already had to replace the ABS module, and the Airbag module in this car due to other issues.

 

After some more digging I've found that the system is putting out 9 volts for the 5 volt reference circuit which would certainly cause those codes to come up. I'm thinking the ECM is bad. I'll keep posted as to what I think the issue is as I dig around the car.

 

Confirmed the ECM is bad. The ECM was seeing 17.9 volts and outputting 9 volts because it thought more was coming in. Alternator showed 13.5-14.volts and the ECM power wire also showed 13.5-14 volts coming in while the car was running. Sending a good used ECM and my original off to Digi Controls in Canada to pull the old info and install the used box. About $200 + shipping!

Also, fixed the lack of dome lights, power sunroof, and power locks. The siren was bad in the fender. Picked up a good used one and it worked perfect.

If you guys need to get stuff reprogrammed I highly recommend Digi Controls, the guys are super smart, fast service, and a reasonable rate. It takes a little time in shipping because they are in Canada, but it's well worth it!

I had a bad airbag module in the same car that the pins were melted together on the CAN circuit due to water intrusion from seepage out of cup holder. I pulled a good used Airbag module and sent it off to them. A week later I had the reprogrammed used module and it worked flawlessly. Can't thank them enough lol