ABS light / Brake failure message

[Wilse]

Hi folks, first post here and looking for some help with this D5. Please be gentle. I am no mechanic, but confident with replacing parts, and have home maintained cars for best part of 20 years, although it's not as easy as it was.

Car is 2005, 2.4 D5 163hp with 121k on clock

Current issue is with the ABS.

info:
ABS lamp lit
Anti Skid message

synopsis:
Abs lamp stays on constant. When moving away from starting car, speedo sticks at 20mph, revs constantly increase, no gear change (in auto)
If I switch to manual, gears change ok, but speedo still stuck at 20mph regardless of road speed.
If brake pedal depressed 3/4 times before driving, after 1 revolution of wheels, I get BRAKE FAILURE - STOP SAFELY message and BRAKE ASSIST SERVICE REQUIRED messages with red triangle. However, car then drives fine, gears change in auto OK, and speedo operates correctly

Had it plugged into Vida -
Following codes presented RED

BCM-0021 Wheel Sensor, Right front faulty signal
BCM-0041 Wheel Sensor, Right rear faulty signal
BCM-0094 Communication between control units Communication problem with DEM

and these AMBER

BCM-0042 Wheel sensor, right rear mechanical error
BCM-0109 Communication between control units communicational problems with SAS, internal fault
BCM-0031 Communication between control units Tolerance control for SAS not run
SAS-0007 Control module internal fault
SAS-000E Steering wheel angle sensor internal fault

I have replaced the front right abs sensor, and checked reluctor rings for damage (this one recently replaced <1000mls ago, temporarily clearing ABS lamp lit)

Is it likely to be combination of 2 sensors with faulty signal causing this BRAKE FAILURE message? or is it possible its a fault with a module, given the unusual trigger for fault messages?

Any help greatly appreciated

[ggleavitt]

If you have VIDA and can read the car, you can see the troubleshooting sections for these codes, even run a few tests including the diagnostics and live data on the steering angle sensor (SAS) if it's really working. You can also see history on the codes, see what's been reported and when. Start by walking through all of the red errors, read the conditions/symptoms plus the action the car takes on activation of the error. Also check https://xemodex.com/us/diagnostic-flow-charts/, these folks have a decent troubleshooting workflow for both BCM and DEM, should it be warranted. And for sure check module connectors for corrosion before you get too far along.

Speed thing is weird, my guess is it stays in first and won't shift up. Might be a honked up CAN bus when that occurs. Are there any other codes being reported in this car ? I would have assumed a TCM code might have gotten spit out as well based on the scenario you describe.

[Wilse]

Thanks for that. Only other codes related to the climate system, which is not a concern at this point.
I dont have my own vida, had a local owner read codes, hence coming here for other peoples experiences.