Hello, first post. Picked up a 124,000 kms 2006 R53 a while ago with the trifecta issue known at the time of purchase. Scan details show left front speed sensor and real time data while under way showed it reading 0 while all other corners indicated accurate speeds. So, low hanging fruit, I replaced the sensor with no resolution. Replaced the hub, same. So I pulled the new sensor to see if it could be that the old crusty hub damaged it and the end was slightly abraded and I could see the smallest bit of metallic something on the end (really small). I did raise up the sensor prior to removing the old hub when replacing the hub but could it be that the new sensor was damaged when driving by the old crap covered ring on the old hub ? Are they that delicate? Thanks in advance.

 

PS, I'm not sure how it is here but on the pelican air cooled 911 forum you justifiably get hassled if you don't post a pic of the new car so here it is.

 

I don't know if they are delicate, but they sure are sensitive. I had the same issue with the trifecta. I replaced my "old" wheel speed sensors (I say "old" in quotes because the previous owner had just replaced them), with new Hella brand sensors that I got from Rock-auto. Unfortunately, I still had the issue after replacing them (intermittent TCS, tire, ABS lights) and was pretty miffed. By intermittent I mean, they'd turn off on the way to the store, then come back on the way home. But, they would never stay off for more than a short trip to the gas station. And if I went more than 5 miles, they'd definitely be glaring.

I went auto-crossing and was a bit upset that I'd have to run without ABS because of the light. I swapped over onto my 200 treadwear Falkens on OEM wheels and headed out. I thought I got lucky that morning because the lights didn't come on. Those pesky lights stayed off ALL event and even on the way home!! When I switched back from my autocross wheels to the daily wheels that came with the car, I noticed the hub bore diameter was larger on the daily aftermarket wheels than the OEM wheels that my Falkens were on.

As soon as I switched back to the non-OEM wheels and ran to the corner store, the lights came back on. The wheel was centering on the bolt pattern alone and not the hub. I ordered hub-centric rings to solve the centering issue as well as an imbalance/bad shake that I'd get at 65-75 mph and BOOM...the intermittent TCS, flat tire, ABS light hasn't returned since. Its been a couple weeks now and no lights.

So, if those durn sensors can sense a slightly off center wheel as an issue, I'd guess that an abrasion on the sensor could cause you an issue. Good luck.

Edit: Oh, and you said it was reading zero. Did you by chance hit the blue connector with some electrical connection cleaner and plug/unplug it a few times to make sure you had a good contact?

 

Hi, no I haven't fiddled with the blue connector and feel dumb for not doing so. I will give that a whirl and see if it helps.