2013 XC90 with ABS/DTSC problems

[xcwilliam]

Hi all,

I'm just hoping for a little advice with some problems I am having with my XC90. It is a 2013 D5 model.

One day the "Brake failure - stop safely" message came up. This was followed with the red triangle symbol, red exclamation mark light and the ABS and traction control lights being illuminated. This was occurring intermittently at first with no warning lights on some days but now it is on most of the time.

It is also noted that the heated seats aren't working and the headlight levelling isn't working. Running the DTC check from within the car shows BCM NOT CHECKED

I have checked all the fuses in the CEM, REM, side of dashboard and under the bonnet all are fine.

I have scanned the car and found the following faults
Gearbox ecu
-CAN TCM ABS circuit malfunction
-No communication with BCM
-Pressure sensor brake servo faulty

CEM
8F12 -CEM beam adjustment
1A5F - Communication with BCM
1A67 - Headlight control

CCM
DD30 - Seat heater right faulty
DD12 - Seat heater left faulty

Engine ECU
- Brake pedal travel sensor circuit

BCM - unable to connect

On checking the CEM for voltage, I see no voltage at the seat heater and bcm/tcs fuses. The other assorted fuses on the CEM do show voltage. However, on days where the fault is not occurring, I see voltage at bcm/tcs/seat fuses as normal.

Tried charging the battery fully, and alternator is outputting 14v+ so assume all is well here.

Oddly, sometimes when I clear all faults within the gearbox and CEM everything starts working again for a short time.

I am not sure if this is a faulty CEM, or BCM or something else

Sorry for the long post, trying to include as much info as possible and thanks!

[xcwilliam]

Apologies for bumping this old thread, but just updating with the fix in case anyone comes across it.

The problem is caused by a relay in the cem. The circled relay in the attached image is the culprit. You can test if this relay has failed on your car by turning the vehicle on and looking for a live fuse on the cem, when you find a live fuse run a wire from the live fuse over the the abs fuse. Your abs warning lights should go out temporarily when you do this.

The relay code is Tyco VZ23134-J52-X455. I code not source a new one so I bought the cheapest cem I could find and desoldered the ones on it (the xc90 cem has two of these relays so you should have a backup)

To fix, remove cem (YouTube). Open plastic casing of cem, find and desolder the relay circed in the attached image. I found the desoldering difficult and you will need a hot air station. Solder in replacement relay and reinstall cem.