CEM Communication problem during start-up

[SVG70]

On my 2009 V70, I am having this very weird problem that I can't find similar issue anywhere on the web. Basically when I start the car, none of the window control, radio control works. The tachometer and speedometer needles don't move. Then when I start driving the car, after about 30 second to 1 minute, all sorts of warning lights (SRS Airbag, Brake, ABS, traction control) start showing up on the dash for about couple seconds and then all went away. Then window control and radio control would start working.

This problem started happening after I replaced alternator that I bought from RockAuto. I tried to replace the voltage regulator on that new alternator with genuine Volvo one, it didn't fix the issue. I also replaced the battery (my old battery was 5 years old) and it didn't fix the issue. I did disconnect both battery terminals before working on alternator every time. The car runs fine. It's just very annoying that I can't operating anything the first 1 minute or so during driving. Also, when I turn off the engine, I can't lock the car most of the time. Seems like the car lost communication to the door module sporadically.

I did try to hook up VIDA and found these error codes.

CEM-U015500 Lost Communication With Driver information module
CEM-U015600 Lost Communication With Infotainment control module
CEM-U016400 Lost Communication With Climate control unit
CEM-U019900 Lost Communication With Driver door module
CEM-U020000 Lost Communication With Passenger door module
CEM-U020800 Lost Communication With Power seat module
CEM-U015100 Lost Communication With Supplemental Restraint System Module
CEM-U001000 Medium Speed CAN Communication Bus
PB-U014000 Lost Communication With Central electronic module

I tried to erase these codes but they kept coming back. I checked the CEM cabling under the glove box on passenger side and they all look pristine. I checked alternator voltage and it's reading between 13.38V and 14V.

Is this the new alternator that's causing this communication problem? Or something more serious wrong with the car. This problem doesn't happen when I drive the car, it only happens when the car is in idle after starts up or turned off.

Please share your opinions. I'd appreciated it!

[jamespirtle]

Hello,
I think poor grounding can lead to communication issues between modules. Inspect all ground connections, particularly those related to the CEM (Central Electronic Module) and the alternator. Clean and tighten any loose connections.

[scot850]

Does your car have a fusible link to the BCM from the battery? If so it is failing and needs replaced. Volvo sell a replacement cable and link that you swage into the cable to the BCM which controls all you cabin electrics.

Neil.