ABS / Brake Failure light & message
 

Hi folks, first post here and looking for some help with this D5

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 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

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 unitsTolerance 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

Physically inspect the ABS wheel sensors and reluctor rings for damage

Unplug the DEM and check connector for corrosion
Check DEM fuse
If these are OK, remove DEM, open up and inspect for corrosion

Front rings look ok, cant see any obvious cracks or missing teeth. The rears are magnetic though?

this is the front ABS sensor I removed.

sorry, correct image

DEM connection looks fine, no corrosion on pins of connector. clean inside (forgot to take pic though!)
Fuse 7.5a (AWD #23 in rear fusebox) awkward to get to, but pulled it and is good.

Can i take the DEM off without leaking fluid though?

If you see nothing obvious than follow the diagnostic procedure given in VIDA

An osilloscope is worth more than an entire toolbox when dealing with ABS signal issues

I don't have access to Vida, I had the car scanned by someone with a Vida setup for the codes.

So looks like I have to change the wheel hub and rear sensor and hope for the best. Garage want £300 to do it, reckoning parts stand me around £120, might have to suck up the stripping out of the seats and hope the hub comes out without too much hassle

There seems to be a lot of ABS faults on these pages, but not many fixes?

You are guessing.
Using guesswork as a diagnostic precedure often results in replacing perfectly good parts with parts you did not need to buy, thus costing more time and money than necessary.

Example: you may have a cracked reluctor ring, but you might fit a new ABS sensor and thus not solve the problem, resulting in unnecessary costs.
Or you may have a wiring loom issue, and you only find out after fitting a new hub and new ABS sensor, again spending more than you need to.

Or it may be something completely different.


I recommend to stop guessing and start diagnosing
Diagnostics is a lot more than just a one-off code read.
It involves resetting codes, running drive cycles, reading the codes after the drive cycle, reading live data, and looking at signals on scopes and meters, sometimes deliberately inducing faults such as disconnecting sensors to observe what happens, and using other logical steps and a lot of common sense.
And that all happens before you order new parts.


But it is a free world and you are a free person who can choose to do what they want, so at the end of the day the choice is yours.

Thanks for the input. I am aware i can make my own decisions, I came here for advice. Clearly investing in hundreds of pounds of technology is mandatory if you own a 14 year old Volvo and there are no common failures experienced by other owners.
I agree that Volvo dealers are prone to guessing at great expense also, so figured the demo
graphic of users on here would be a useful point of reference. Thanks for the warm welcome

I am giving you advice. But take as as you want. No skin of my nose.

Now you are making broad sweeping assumptions that are completely misfounded.

The right tool you need (VIDA) will set you back about much much much less than "hundreds of pounds".

If you wish to do any repairs on your Volvo yourself, the first tool in your toolbox needs to be VIDA.

Contact cheshired5 on this forum.