"Brake Failure" Messages after AWD Delete

BigBean · Post by **BigBean** » 10 Nov 2020, 07:11

Hi guys,

Hoping someone can help shed some light on how to clear this message.

Recently deleted the Prop Shaft, Rear Diff & CV Shafts in my 03 xc70 to convert to FWD.

Since doing so, it drives perfectly fine in FWD, but I get a "Brake Failure, Stop Safely" messaged and an ABS light.

I'm trying to figure out how to remedy this and having a hard time finding any info online about this specific issue.

Appreciate any help.

Post by **jonesg** » 10 Nov 2020, 22:25

BigBean wrote: ↑10 Nov 2020, 07:11 Hi guys,

Hoping someone can help shed some light on how to clear this message.

Recently deleted the Prop Shaft, Rear Diff & CV Shafts in my 03 xc70 to convert to FWD.

Since doing so, it drives perfectly fine in FWD, but I get a "Brake Failure, Stop Safely" messaged and an ABS light.

I'm trying to figure out how to remedy this and having a hard time finding any info online about this specific issue.

Appreciate any help.

You eliminated the rear CV shafts?
if the wheel sensor pulse magnet is located in the inner bearing hub then it might not be rotating without the splined end of the CV shaft turning in there.
Well I just looked at the old bearing carrier I removed, maybe the pulse generator is part of the inner bearing race, without the shaft the inner race will not rotate.

I ended up in a snow filled ditch 2 yrs ago, got towed out and had ABS light plus brake failure warning, the front end was caked up with snow, after it melted away the warnings went away. Probably snow interfering with the tone ring or something similar.

Post by **darrylrobert** » 10 Nov 2020, 23:18

you deleted the rear diff?...wow thats alot of work...why? i also think its got something to do with the rear sensors. might need re-programming??

BigBean · Post by **BigBean** » 11 Nov 2020, 10:37

Update: tried new sensors and also have fwd hubs on there and still no speed reading in VIDA. Interestingly the fault will not happen while VIDA is connected, and I can look at the sensor output. Both rear abs sensors rear 0.6 km/h (nearest value to 0). One side is a fwd hub and one side is the awd hub without shaft. (Only for testing purposes, once solved will have proper matching hubs)

If I connect VIDA after the fault, it will say faulty reading from both rear abs sensors.

From my research it appears the sensors are the same part between fwd and Awd. Which leads me to try to find where the reluctor/tone ring is located on FWD cars to see if I can install/replace whatever it is.

BigBean · Post by **BigBean** » 11 Nov 2020, 10:39

darrylrobert wrote: ↑10 Nov 2020, 23:18 you deleted the rear diff?...wow thats alot of work...why? i also think its got something to do with the rear sensors. might need re-programming??

Not that much work..
Got the car for $300 as a winter beater, rear diff was basically seized, center support bearing for prop shaft was beyond dead.

Figured I'd rip them out to get it rolling in FWD while piecing together another and system.

If you have any idea the relation between AOC control (rear diff) and the ABS sensors you'd be a huge help haha.

BigBean · Post by **BigBean** » 11 Nov 2020, 10:42

jonesg wrote: ↑10 Nov 2020, 22:25
You eliminated the rear CV shafts?
if the wheel sensor pulse magnet is located in the inner bearing hub then it might not be rotating without the splined end of the CV shaft turning in there.
Well I just looked at the old bearing carrier I removed, maybe the pulse generator is part of the inner bearing race, without the shaft the inner race will not rotate.

I ended up in a snow filled ditch 2 yrs ago, got towed out and had ABS light plus brake failure warning, the front end was caked up with snow, after it melted away the warnings went away. Probably snow interfering with the tone ring or something similar.

The shaft missing makes sense, but I do have a fwd hub installed with same results. The FWD hub must be able to produce the signal without a shaft obviously, so I'm unsure why it's still not reading.

No snow here yet, nice and dry and ive cleaned the sensor and hub very well with no results.

Post by **jonesg** » 11 Nov 2020, 16:50

the front hub has an external tone ring.
The rear hub has integrated hall sensor magnets or whatever system they use.
I recall the rear hub was quite expensive and they look identical side to side but are labelled unique to each side.

BigBean · Post by **BigBean** » 12 Nov 2020, 10:07

jonesg wrote: ↑11 Nov 2020, 16:50 the front hub has an external tone ring.
The rear hub has integrated hall sensor magnets or whatever system they use.
I recall the rear hub was quite expensive and they look identical side to side but are labelled unique to each side.

When you say rear hub do you mean the wheelbearing/hub assembly? If purchased a new FWD set so I'd assume it should be working at least on the side that's installed.

Post by **jonesg** » 12 Nov 2020, 22:29

yes the rear bearing is part of the hub. The computer is looking for the signal from the rear sensors.
There is no signal because the inner bearing race can't rotate without the drive shaft splines .
Thats my guess.