ABS Break lights ON
 

I have a 2001 X5 4.4i. 130 miles after the two front axle assembly replacement, ABS and Break light comes on, Speedometer stopped, Techometer momentarily working, temp needle goes to max. After some web search, I decide to test the ABS Speed sensors myself.

After disconnecting the sensor connector in the wheel well, I measured the voltage coming out of the ABS module:
0V - ignition off; 2.8V - ignition key pos 1; 2.5V - ignition pos 2.

Measured the resistance across the sensor terminals:
Left front - 8.5MOhm; Right front - 8.2MOhm.

Attached a scope to the sensor output, spinning the front axle, I do not see any pulse coming out of the sensor.

Removing the sensor from the hub assembly, found iron powder on the sensor tip. cleaned sensor tip. Placing a magnet at the tip of the sensor and moving magnet, barely see any voltage change.

Looking into the sensor hole, spinning wheel, I do not see anything different after 360 deg rotation. It was just a metal drum. So what causes the sensor to pickup signal?

Now I am wondering if the sensor is bad, or installation of the axle causes the hub assembly to fail? :whistle:

Thanks in advance for your help!

//Leo

Leo,
I just had to replace my wheel speed sensor on my '01. I had some of the same symptoms as you, speedo would not work, ABS light on, brake light on and also traction control light on. The only thing is that the wheel speed sensor is actually on the right rear wheel. I believe that all the wheels have ABS sensors, but the speedometer is controlled by the right rear wheel. So to answer your question if your installation of the front axles would cause this, I would think the answer would be no. I have heard of some of these symptoms also being caused by a faulty ABS Control Module, which I had mine rebuilt also. If someone else has any more to add please chime in. Hope this helps.

Todder

Hi Todder,

Thanks for the response. I posted and paid for an answer at www.justanswer.com. The answers I got back were
1. Speed sensor is on the left rear.
2. The problem is not likely the ABS sensor, but the instrument panel cluster since techometer and temperature meters were off. Need to run a diagnostic to pin point the problem.

I did not get an answer on if the sensor resistance was within spec. In addition, I also measured the left rear - 4.5MOhm, which is half of the front wheel sensors. Anyone knows if the sensor is OK? Thanks in advance for your help.

//Leo

does the trans fail safe prog come on? i have the exact problem that you have except i have the trans message flashing every second and my acceleration is sluggish. my car is currently at the dealership i'll let you know what they found out about my car..if that helps

2001 X5 4.4 Break ABS lights on
 

I do have the "Trans Fail Safe Prog" and sometimes "Engine Fail Safe Prog".

After I posted message, for two days, each morning when I first start the car, everything seemed to be normal, only "Engine Service" light on. But after driving 10 - 14 miles, the gauges stop and lights are on, Trans going into fail safe mode which is the 3rd gear (it makes acceleration sluggish, best to drive at 45mi/hr). Other symptoms in fail safe mode: Temperature gauge works momentarily (sits in red most of the time), techometer works momentarily, instrument display goes into dimmer mode and intensity not adjustable.

It makes me think the failing has to do with some timer or temperature. When cold everything is OK.

I will take it in for a diagnostic run next week when my friend has time. Will update the findings.

In my personal experiances and observations with E53's, faults for wheel speed sensors go like this...

Either front sensor, usually just the sensor.
Right rear sensor fault usually the DSC module.
Left rear sensor faults usually the Instrument cluster.

As for diagnosis, I think you are looking too deep, these measure fron the side of the tip from the back of the wheel bearing, and the micropulses are harder to read even without a graphing ocilloscope due to the size and frequency. Just simply read which side the sensor fault is on, swap the sensors left/right for either respective axle, clear faults then drive. If the fault followes the sensor, replace the sensor. If it stays in the same position, check the wires between the sensor plug and the DSC module if needed before buying the components mentioned above.

That is the good thing about both sensors being the same for each axle, just swap them for diagnosis.

This is the methods I used when diagnosing my own truck (which needed a DSC module, r/r sensor fault) and my mothers E39. (which just needed a front sensor)

Since instrument cluster was in question, I had the cluster replaced since it was loosing pixels. Parts covered by BMW USA good will program, I paid labor. The error did not go away, so engine diagnostic showed DSC module error, electronics part. BMW would not cover the DSC module cost. I could have the DSC unit rebuilt, but that will put me out for a week and I need the car for prearranged business.

It turn out to be a VERY expensive repair. It could be worse without the BMW good will.

Is it ABS or DSC module?
 

Good write up. My car operates normally for first ten minutes, then ABS and
DSC yellow lights and red Brake lights come on. The Speedometer also goes out when the lights come on. I have checked and cleaned
ABS sensors before when I had similar problems which corrected issue.

In reading info on the modulemaster website they seem to think it is the ABS module which they will rebuild for $300. I've heard talk of the steering angle sensor.

What symptoms if any does a bad DSC module exhibit??

Thanks for your help! PS I have 218,000 on my 2001 X5 I bought new.

The steering angle sensor wouldn't have anything to do with the speedometer, so you can scratch that of the mental checklist. As for the bad DSC, they all fail individually and will exibit slightly different symptoms. If you want to be extra sure it isn't just the sensor you can swap it with the right rear and se if the fault follows.

As far as the left rear sensr circuit quitting, causing the speedometer to quit... It could be the cluster or the module, you got a 50/50 chance. I'd consider having diagnosis done by the dealer (and ask for a master tech) to see if there are any CAN bus faults as often the the module dropping out can cause can communication faults to be stored. The dealer has enough diagnostic resources to be able to better know which it is causing the issue through testing.

I've been thinking it is the ABS module
 

modulemaster's website made the comment that if the car operates normally and then the lights come on and the speedo goes it is temperature related.

Mine works fine until it comes up to temp, maybe 10 minutes. Then speedo goes and lights come on. It seems if it were a bad sensor this wouldn't be the case.

What I don't know is BMW control logic. It must be polling devices on some regular basis at some pre determined interval. If they fault once some circuits need to be cleared, like oil change interval. In my case I'm just wondering if there had been a transitory fault it has been stored in the computer and will keep showing lights until it is cleared. Then I wonder if nothing is wrong, just the fault circuit.

At my mileage I don't really care about ABS. I have a GPS so I know my speed anyways without a Speedometer......just kinda annoying when stuff doesn't work. To show my mentality when my check engine light came on years ago I did the gas cap thing and in the end put a piece of black electrical tape over it. Ditto when the airbag warning light started to come on intermittently........more black tape........may have to get it out again!

I like the BMW ride, but I do think the complexity of their electronics and their propensity to fail after 100,000 miles really detracts from the vehicle. The motor and transmission have been bullet proof other than all the oil gaskets that had to be replaced.