Speed Sensor ABS issue
 

Hi all, just hoping someone can share knowledge/experience of an ABS issue I’m currently having.

2005 A8 3.0tdi.

I have an error for my front right speed sensor - G45 - implausible signal - sporadic. I also have the 0003 error for the ABS unit but that has been there for years and never been an issue, I’ve read that this code is quite common. (I don’t have VCDS but do have software adequate to read codes.)

It began with occasional ABS/TCS lights with parking brake, then my speedo and power steering started to play up so I changed the sensor for a Bosch sensor. I had to tap the old one out with a pick as it sheared.

Within about 50 miles the ABS/TCS and parking brake light illuminated again so scanned and got the same error, so I fitted another replacement sensor. Began driving and below 10-15mph I can feel the ABS kicking in then over that speed the ABS/TCS lights illuminate permanently and the parking brake above 10-15mph (as before), these go away when I switch off the car and appear after starting and driving above 10-15mph.

Now I don’t think this is an issue with the actual sensor as I’ve changed it twice now, I checked the wiring quickly but not unwrapped any of it fully as I don’t think it’s that as the sensor fixed my speedo/power steering issue.

I’m thinking, what are the chances that I’ve tapped too far whilst getting the old sensor out and have damaged the ABS ring? (I was as careful as possible but it was tricky as it’s difficult to see in there). If so, is there anyway of checking this? I can’t seem to find any info online on this.

If anyone had any other suggestions on what to try I’m all ears.

For info, parking brake is still working fine, even though the error appears.

Thanks,

Dale

I currently have an ABS/ESP/Parking brake issue which arose from a dead battery whilst I was away however it was charged and driven, no problem. It sat for another week and was still fine, drove with no issues. The next day I went to move it and all the lights illuminated. VCDS shows a control module defect and speed sensor for the N/S/R but on inspection I don't think there is a rear left sensor, only front left and rear right, unless I'm going blind lol.

Having done some reading, the ABS can throw false speed sensor faults so I'm putting it down to the ABS module or wiring. I too haven't yet checked the wiring but some online reading suggests the wiring can be the issue so needs to be stripped back into the wing and inspected. Yours doesn't seem as bad as mine as you still have the parking brake, mine errors due to the ABS and doesn't work.

Definitely check the wiring first. Unfortunately it could well be your ABS ring/hub that is causing the issue. I think the bearing can also cause the issue but don't quote me on that

Thanks, yeah I’ll probably start having a look at the wiring this weekend.

To be fair the car has barely moved now in weeks so could possibly be the battery but I’m doubtful as there are no other issues, although I did get the battery management warning last week.

Oh, there are definitely 4 sensors. I believe front right and rear left are the same and then front left and rear right are.

I’ve heard the bearings can be a nightmare to replace so not sure I really want to tackle it if I can help it but I believe it needs to be done if the ABS ring is the issue (not 100%).

I wonder if the S8 (or facelifts) were different? I checked online videos and then went over the rear hub on the left, no wiring and no sensor :Confused:

Bearings are not the easiest jobs, but having the correct tools definitely helps. I would probably leave that for the experts.

You might want to do a continuity check on each of the pairs of twisted wires from the Brake ECU to the Calipers to see if that throws up any issues - I ended up replacing each twisted pair with my car to all four corners as the casing on the wire was intermittently cracking and exposing wires which then touched and threw up faults at all sorts of times. The worst wires were those closest to the engine where heat had affected the wire casings but as we didn't know how far the problem went it was reasonable to just replace all of the abs wiring from each wheel to the Brake ECU. Haven't had the issue come back since doing that . . .

Cheers both.

Unsure about the facelift cars being different, my 05 facelift definitely has sensors all round as I’ve replaced a rear on it.

I think wiring will definitely be next, continuity check is definitely a good shout, cheers for that! I’ve had a quick check of the wiring at the ABS module and the wrapping does seem very brittle so just need to find time to unwrap it all.

Just a thought, the sensor(s) I’ve replaced it with have been Bosch sensors but not genuine Audi parts. I.e. the one I took out had the genuine Audi stamps as well as the Bosch but the new ones only have Bosch. Do you think this would have any bearing on the sensor working as it should? I’m unsure whether it’s worth getting a hold of a genuine sensor and trying that.

Cheers

I had an ABS sensor failure on my previous Mercedes. I was going to replace with a Bosch (not sure what the OEM was) but was advised on Mercedes forums to only replace with genuine. This was from respectable Indies who had replaced lots of these and have seen issues arise from aftermarket sensors, even reputable companies like Bosch. I don't know if the same would go for Audi but I would be inclined to use a genuine part as it rules out a faulty sensor

Yeah could be a good shout, and would at least definitely rule the sensor out. I only ever tend to use genuine parts when it comes to sensors but would’ve assumed with the Audi one being a Bosch one it would have accepted the same brand but I have read that sometimes the aftermarket ones aren’t the same quality.

Reckon I’ll start with the cheapest/easiest options and work my way through!

Cheers

Thought I’d update this with the solution, in the case that anyone refers to this thread in future with a similar issue.

I purchased and fitted a brand new Audi sensor with no luck. Tested the connection which was fine. Did a rolling test using OBD11 which showed the offside front sensor only picking up speed on every rotation, other than that it was stuck at 1kph.

Bit the bullet and dropped it in at a specialist to have the wheel bearing replaced as it’s not a job I wanted to tackle myself. They confirmed it was indeed the abs ring (or what was left of it) that was causing my issue. An expensive fix at £350 to supply and fit the wheel bearing!