I have an 04 r50 that is giving me the p0500 code and the triple dash lights (check engine, abs, and tpms). I read up on the wheel speed sensor all over the Internet but can't figure out how to determine which one is triggering the code.

Thought about just measuring the static resistance of each but wasn't sure if that would work.

Anyone have any suggestions?

 

Could hook up to a scope and spin the wheel and look for the pulses - that will work.
Using a sensitive multimeter would probably pick up the blips as well.
Set for lowest voltage range, analog (needle meter) will be easier than digital.

I think the dealer accessable diagnostics (not the OBD-II stuff) might store a code that tells,
but not sure about that.

No idea what the resistance on a good sensor is, but if 3 of them are xxx ohms and the other is
0 or ∞ (short or open), that would be a good clue.

If you do measure the resistance, post your results here, please.

 

Here's a good reference that applies to E36 BMWs.
The harness pin schematic is probably different for the MINI.
http://www.bimmerboard.com/forums/posts/1071676
Looks like the BMW MINI ABS wheel speed sensors have a resistance
of about 1 ohm.

 

You can measure them all, but have someone with the BMW computer read the code and it will tell you exactly which one.
Even if they charge you, its cheaper than buying more than one wheel speed sensor.

 

Thanks for the help guys. I measured the front passenger side resistance and it was 6.5 mega ohms. I suspect that is way high. I'll try the rest. I have an oscope and I'll try to get a read on the signal under operation. That will be a little difficult unless I try to run the car while on jack stands. I'll try to come up with something...I'll post when I get it going.

I was hoping I could read the signal from the OBD port. I have a wifi obd interface that gave me the code, but couldn't access that data direct...that would have been awesome!

Thanks folks...stand by for more later this weekend!

 

You can jack up the wheel and just spin it by hand with the shifter in neutral (front)
or ebrake off (rear) make sure you chock the diagonal tire.
6.5 M looks like an open circuit - that one must be bad.
What do the other ones read?

BTW, I tried to find info on the pinout for the MINI ABS module with limited success.
The pins are probably a little easier to access than probing the insides of the connectors to the sensors themselves.
According to the Bentley wiring diagrams:
sensor 1 - pins 33 BR, 34 GE (letters are color codes for wires)
sensor 2 - pins 46 BR, 45 BR/RT
sensor 3 - pins 42 GE/SW, 43 GE/BR
sensor 4 - pins 37 BR, 36 BL
BR brown
GE yellow
RT red
SW black
BL blue
No info on which number sensor goes with which wheel.

 

First off....thanks Cristo for all the good info.

Here is what I did:

I pulled the front drivers side sensor and measured the resistance...6.9 MOhms. Fairly consistent with the passenger side. I turned on the key and measured the voltage feeding the sensor....it was your standard 12 volts (roughly).

I decided to just feed the sensor with an external 12 V (extra car battery - fused of course) and put a scope on the sensor while I spun the wheel. This way I wouldn't have to pierce the wires or anything and have the car running or at least the key on.

I've posted the video of the waveform here online:
https://picasaweb.google.com/lh/phot...o78?feat=email

So the driver's side is good. When I did the same test on the passenger side, I got nothing! Now, the only concern I have is that the static resistance is similar. with that in mind, I checked the voltage going to the sensor from the ABS and confirmed that it had 12V. So maybe the sensor is just not picking up the keys on the hub.

i'll let you know when I get the new part in to confirm that everything worked.

Thanks again! Here are some pictures as well:

Picture of the hook up at the sensor-



Picture of the setup at the scope-



Picture of the probe (piece of bent wire) I used to hook up to the sensor pins-



Picture of the probe hooked up on the sensor-

 

I tried several methods but I ended up going to a mechanic friend that has a snap on diagnostic computer. He hooked it up and after driving a block or so he told me which one was bad.

 

Never hurts to do a visual inspection - when one of mine went it was simply because of a sharp bend/break in the wire that was obviously visually.

- Mark

 

Success!....replaced the passenger side front speed sensor and everything works great. Actually, the sensor pulled right out which surprised me...i was expecting it to be a pain to get out. all is good....no codes and no warning lights and since it was raining last night I was able to easily test the ABS...PERFECT.

$35 part from JC Whitney!

 

An old thread, but I am chasing the same problem. Got the dash lights on whenever it rained, and replaced both front sensors (cheap non OEM parts) shortly after I did clutch work, but the light went from intermittent to solid on.

That front drivers side driving light isn't getting power either, so I'm suspecting a problem with that wiring harness branch. I dissected it pretty far back from the wheel well, and haven't found the break yet. Could be a coincidence of course, they could be independent problems.

I've spent a few hours now trying to hunt down schematics and pinouts. It's a mess. The links to the other sites that claim to have it won't work with modern browsers, the Ebay service DVD I bought didn't include schematics for the 2005 R53, and that virtual machine on that DVD can browse out to those online WDS manuals with a frozen in time browser... and the navigation tree finally shows up, but then when you try and pull up an actual document it goes to a file hosting site with a 404 file not found error. Frustrating, but you get what you pay for I suppose.

I'm hunting the schematics, but in the meantime, this is the best thread so far on the topic, so I thought I would build on the great information JWP so thoughtfully included already. Thanks!

I'd rather test it from the ABS controller side, so I can put the scope up there and monitor the signal with everything hooked up and intact. But not a big deal to do it from the wheel side either. I'll make notes and share here.

Thanks again for taking the time to shoot pictures from your scope and the pinouts JWP!

 

Lots of work, but little progress. Still haven't found a reliable source for schematics. Got a $20 code reader that didn't work to get ABS codes (PEAK R5 EMX MINI Scan / Reset Tool For R50 R52 R53 2002 - 2006). Then got a less cheap amazon prime code reader that appears to work nicely to get the codes.




No fuses blown.

So now I suppose I'll track that back to eliminate some easy stuff before assuming that the whole ABS module is bad (though I suspect that is the case). I'll hit that front left corner and do some wire harness dissection, inspection, and re-armoring, and try and intercept signals with the scope to confirm sensor operation.

I'll perhaps start a new thread for that, as this one was more specific about just the wheel sensor, is pretty old, and it looks like my problem may be bigger than that.

 

Just to be clear on this - those sensors have diodes in them. A simple resistance or voltage measurement is not sufficient. You can see the pulses using an oscilloscope (if you know what you are doing) or read the wheel speed data through OBDII in real time with a better code reader or INPA/DIS.

And, being cheap, I tried the bargain wheel speed sensors and had nothing but trouble. Look for the better quality aftermarket brands (PEX seems to be the cheapest with reasonable quality).

You can always switch sensors Left and Right and confirm the fault follows the sensor before spending money. Switch them, clear the codes, see what pops up again...

 

Sorry, I should have followed up with my solution back when I fixed it..

The speed sensors are hall effect semiconductors, so as David says, you can't do any kind of effective static test on them. And they "read" a magnetic ribbon built into the bearing that has a bunch of magnetic bands built into it, so you could have a perfectly good sensor, but damage to the magnet or bearing that is causing the problem.

The scope setup above would do it if it's really badly failed. But my failure was hit and miss, I would have to drive for several miles before it would come back with the error after I cleared it.

I finally traced it down using that tool pictured above. In addition to just the detailed code (shown in the screen shot) I found it also has a built in data plotter. So I could hook it up without disconnecting any wires, put it in "plot" mode for a particular channel, and drive around. When it failed, I would see a spike to zero in the plot.

It worked great, and I think that was only a $80 tool or something. It doesn't do everything that I hoped it would do, but it nailed this problem and it could clear the ABS light as well.