CEM Question- 2012 XC90

[ttreat1]

Hi All,
Help! I am new to this forum. I did some searching but didn't find anything that answered my questions.

My daughter's XC90 has been acting up with symptoms that are listed in other posts about the CEM. It has been giving the Anti Skid Service Required warning, Brake failure, etc. and then proceeding into limp mode. If you shut it off, it starts up again and everything seems fine. It might go a day or more and then you get the issue again.

I purchased the Volvo software for my Foxwell NT530 which allows me to communicate with the modules. At first I saw a U0100 code for CAN communication error. This code seems to come up as it goes in limp mode. I cleared that error but cannot get any live data from the CEM module. All the values in the live data read N/A. I can get live data in all the other applicable modules.

I have disconnected the CEM, cleaned all the connections and reinstalled. I didn't see any signs of water ingress or corrosion.

Strangely though, I can do active tests within the CEM on any component. For example, the DRL lights are not coming on. I also can't communicate with the Headlight Control Module within my Foxwell. But I can do an active test within the CEM module and turn either of the DRL lights on. I also seem to have full function of everything in the car. I am perplexed. How can I not get live data but I can still test things through the CEM Module?

Does this point to a CEM failure or could it be connection issues elsewhere?

[ttreat1]

One more data point to add... I can see all live data from the rear electronic module. This is bizarre to me since the wiring diagrams indicate the OBDII interface goes through the CEM to all of the other modules. How can I see live data on all the other modules and not see it on the CEM?

Also, I noted that I couldn't communicate with the Headlight Control Module. This happens when I try to directly connect to the HCM module. However, I can get live data from the HCM.

[ttreat1]

Update, I wanted to check the HCM and found lots of water on the drivers side footwell. Tracked it back to the drain on the A-pillar had disconnected. The HCM connector was basically in water. There was another connector in the area that had corrosion. I took the connections apart, sprayed them with contact cleaner and applied dielectric grease.

Now I have my fingers crossed that the issue is gone and additional damage wasn't done.