Wheel speed sensors.....

[OVERKILL]

So, the right rear wheel speed sensor on the 2000 328i went. Tranny goes into limp mode, car becomes an epic turd to drive, as it only runs in 3rd gear when this happens.

Initially, it would only happen once in a blue moon. The dash would light up like a Christmas tree, then it would fix itself.

Then it got to the point where you'd have to stop, shut it off, restart it, then it would be OK.

Now, I get the code immediately after clearing it (the car has been sitting for a bit, wife has been driving the Expedition, I've been driving the M5 and this car also needed a throttle body which is now done and the codes for that have not come back).

What blows my mind is that a bad wheel speed sensor basically cripples this car. If I have one go bad on the Expedition, I'd lose the ABS, whoopdie doo, no huge problem there, but on this car, it is like "Nein Chris, ze veel schpeed sensor ist broken! Ve vill go into ze limp mode jetzt!"

Is this a BMW only "feature" or have others experienced this on other cars?

 

[NHGUY]

I guess you found one of many achilles heels of the "Ultimate driving machine". Tricky people,them Germans.

 

[OVERKILL]

I just find it a touch mind blowing that a bad wheel speed sensor can have such an incredible effect on the car's operation. It's not like it doesn't have 3x other ones to go by or anything...

 

[bdcardinal]

Well you figure it probably has a bunch of digital nannies that use the speed sensors. When one goes out one of those nannies might not be able to keep you from driving like Michael Schumacher, please read my heavy sarcasm. I can see why BMW does it, but it is really annoying when a manufacturer does that.

 

[tig1]

Why does a wheel speed sensor disable the engine this way? I had one fail on my old Merc GM and it did pop a lite, nothing more.

 

[redbone3]

Same reason VW requires a special motor oil, SN ain't good enough for them. Arrogance.

 

[hattaresguy]

Yeah that's how it works with German cars.

The wheel speed sensors are part of a system which controls everything, quite literally. So if one part of that system is out of whack the entire thing goes into limp home mode.

Guys that transplant motors in modern German cars run into this all the time, its a PITA. You either run a stand alone ignition, throttle, and fuel injection system, or you transplant everything. By everything, I mean if your putting a modern motor into an old car, everything, ABS traction control, wheel speed sensors, steering wheel position sensors, body yawl sensors, gauge cluster, everything...This is if you want your electronic transmission to shift as well, it won't shift if as you found out a sensor is off.

This started in the early 90's but really started in the mid 90's, older stuff you can swap around like other cars. Now you have to view the car as a system, and for it to go all the electronic bits have to be talking and agree with each other.

 

[OVERKILL]

Originally Posted By: tig1
Why does a wheel speed sensor disable the engine this way? I had one fail on my old Merc GM and it did pop a lite, nothing more.


Because apparently the car requires feedback from everything in order to operate properly. If one sensor isn't contributing (and this one is FUBAR) then it goes into limp mode until you've fixed it.

Very different approach from my old familiar Ford cars which really don't care.

 

[sleddriver]

Quote:
So, the right rear wheel speed sensor on the 2000 328i went. Tranny goes into limp mode, car becomes an epic turd to drive, as it only runs in 3rd gear when this happens.


That's what's infuriating about the 'digital revolution' in vehicles. Nuts....just nuts.

BMW in english means "Bite My Wallet" according to my indy.

 

[eljefino]

Originally Posted By: redbone3
Same reason VW requires a special motor oil, SN ain't good enough for them. Arrogance.


Yup!

BMW probably knows deep down that a percentage of their cars are owned by poseurs and this internal sabotage is an engineered way for them to get hauled in for service... instead of driving around with electrical tape over their idiot lights.

 

[SAATR]

Had something similar going on with a customer's '98 740iL, except the problem was that he had to put the spare on the car after having a roadside flat, and the spare was slightly over-inflated and less worn than the other three tires. He thought the flat had caused the problem, but the car was reading a SLIGHTLY higher rotational rate at that wheel and BAM, threw him into " limp in". He ended up having to buy four new tires because the one new tire caused a similar problem.

 

[Spazdog]

Originally Posted By: OVERK1LL
Originally Posted By: tig1
Why does a wheel speed sensor disable the engine this way? I had one fail on my old Merc GM and it did pop a lite, nothing more.


Because apparently the car requires feedback from everything in order to operate properly. If one sensor isn't contributing (and this one is FUBAR) then it goes into limp mode until you've fixed it.

Very different approach from my old familiar Ford cars which really don't care.


On the current generation of Mustang, a wire to the instrument cluster dimmer disables the whole car.

One of my younger techs probed a wire, right color-wrong wire....when he did he over probed it and broke the copper strands inside.
The car would not start. I was getting a signal for the starter at the Smart Junction box, but no start. The instrument cluster dimmer took out the whole car.
I do not want to admit how long it took me to find this wire with no continuity.

 

[OVERKILL]

Originally Posted By: Spazdog
Originally Posted By: OVERK1LL
Originally Posted By: tig1
Why does a wheel speed sensor disable the engine this way? I had one fail on my old Merc GM and it did pop a lite, nothing more.


Because apparently the car requires feedback from everything in order to operate properly. If one sensor isn't contributing (and this one is FUBAR) then it goes into limp mode until you've fixed it.

Very different approach from my old familiar Ford cars which really don't care.


On the current generation of Mustang, a wire to the instrument cluster dimmer disables the whole car.

One of my younger techs probed a wire, right color-wrong wire....when he did he over probed it and broke the copper strands inside.
The car would not start. I was getting a signal for the starter at the Smart Junction box, but no start. The instrument cluster dimmer took out the whole car.
I do not want to admit how long it took me to find this wire with no continuity.


OK, now I don't feel so bad, LOL

 

[Win]

On my 90's vintage Jaguars, a bad wheel speed sensor will only disable the ABS.

There must be a reason for a failure putting the car in limp home mode, but it's not immediately clear what it would be.

FWIW, I never really had a "bad" one - they would just get crudded up and a disassemble and cleaning will bring them back to life.

edit: does it have traction control? I can see how it would want all of them operational for that system. But it looks like it could just as easily disable that along with ABS.

 

[HTSS_TR]

Mercedes vehicles have some quirks too. A bad brake light switch will trigger these failures: ESP/BAS & ABS and cruise control. The car is still drive normal but hard braking distance is longer because BAS(Brake Assist System) & ABS was disabled.

 

[JOD]

My Freestyle is exactly the same; both the transmission and Haldex system relay on data from the WSS, and the car will go into limp mode if something goes sideways. So, this isn't a "BMW-only" thing.

My guess is that supposed to prevent damage to other components in the event of the problem with the WSS. I'm not sure I really see what this is such a big deal.

 

[Papa Bear]

Why not just fix the sensor ? ......

 

[Spazdog]

Originally Posted By: HTSS_TR
Mercedes vehicles have some quirks too. A bad brake light switch will trigger these failures: ESP/BAS & ABS and cruise control. The car is still drive normal but hard braking distance is longer because BAS(Brake Assist System) & ABS was disabled.


Yeah, I got blamed for that on an E430.

I did the install. I assure you that I did not touch the brake light switch. No need to. But about 3 months after my install, it lit up all the lights. 1st dealership wanted $4000 for a new ABS pump (blamed it on me for use of "non MB approved electronics"). 2nd service tech fixed it for a couple hundred bucks.(including diagnostic...vindicated me for proper installation of a starter kill device)

 

[OVERKILL]

Originally Posted By: Papa Bear
Why not just fix the sensor ? ......


The part is on order, and wasn't expensive. I'm just surprised at the effect it dying had.

 

[OVERKILL]

Originally Posted By: JOD
My Freestyle is exactly the same; both the transmission and Haldex system relay on data from the WSS, and the car will go into limp mode if something goes sideways. So, this isn't a "BMW-only" thing.

My guess is that supposed to prevent damage to other components in the event of the problem with the WSS. I'm not sure I really see what this is such a big deal.


As I said, I'm just surprised that one sensor (of four) going bad can essentially cripple the vehicle. Not a "big deal", just surprising.

But you answered my question on whether this was "BMW only" or not, so thank you