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Discussion Starter #1
Alright. I started working on this problem trying to narrow in on the problem, and I want to bounce my theory(s) off the board. (pun intended)

I have random occurrences of the trifecta popping on with simultaneous loss of speedometer. So your first thought is the left rear wheel speed sensor is bad. This is still a possibility, but I have other theories. First some more information:

Left rear sensor was replaced in May 2013 and has done approximately 36,000 miles since then.

The problem first started on the drive to TimmayFest this past summer. It seems like I let this go on for a long time but recall the car was immobile for 3 months. :Thumbdown:

What happens is the lights come on, speedo inop, so at my nearest convenience I stop the car and shut off the key for 15-20 seconds. At restart the lights go out and speedo starts working and I'm on my way. This tells me it's a "soft code" and not a hard fault with the sensor. From what I remember when I had sensors go out completely the lights would never clear. Also, more times than not I'll get a slight jerk when the fault happens meaning that the car tried to activate the traction control and then realized it's an idiot and shuts the system down. Since it stops reading from the left rear, the speedo goes out as collateral damage.

I have a CV boot leak from both of my outer axles, so I thought maybe too much grease got on the sensor. Turns out there isn't any grease at all on either sensor. I must also note that I replaced both rear wheel bearings just before Timmayfest using OE parts. See the thread here: http://www.m5board.com/vbulletin/e39-m5-e52-z8-discussion/377633-200k-maintenance.html

Earlier this week I decided I was going to swap the sensors side to side and see if the trifecta and code follows, and if so at least I'll still have the speedo. So I pulled both sides and found the following. The RIGHT side rear sensor looks like it was rubbed on directly by the wheel bearing/sensor. The LEFT side rear sensor looks fine. See attached pics. The bearing pics: the one that is shiny is that one that was rubbing vs the second pic from the left side that wasn't. So I decided not to swap sides as my working theory was that by some chance the left side wheel bearing didn't get seated into the wheel carrier all the way and is on the verge of having too large of a gap between the hall effect wheel and the sensor, causing it to occasionally lose signal and make the DSC think that wheel locked up. The added variable of the right side sensor rubbing at some point complicates things though. (the right side sensor was replaced back in March (12,000 miles ago))

Since I have 2 new (used) axles to go in as replacements for my leaky ones, it will be the perfect time to fix this issue, especially if it means I have to replace a bearing again. I'm not pushing these axles out for a 3rd time! Doing it a 2nd time (hopefully this weekend) will be enough for me!

Have I missed anything? By the way the only code I ever get is for the left rear speed sensor... circuit failure I believe. I'll post a pic if I have one... of course I didn't so I went and ran INPA just now. How do you like my laptop table? Of course to make me look like a liar there is a second code today, as shown. Also had a cruise control code in the DME. My guess is it's from earlier in the week when the symptoms happened with the cruise on, it knocked the cruise off, probably set the codes then.

One last tid bit I just thought of. There was ONE TIME when I was sitting at a dead stop at a red light and the lights came on, when I took off the speedo was inop.

I write all this and over think things because I'd rather try to pinpoint the cause than throw parts at it. This car gets it's fair share of preventative maintenance already and all of the components discussed have been replaced under my watch... except the DSC module.
 

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Sounds like a solid analysis - that speed sensor definitely doesn't look right.
 

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Discussion Starter #3
The sensor that doesn't look right is not setting codes...
 

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Sorry to be a little off topic. I know the sensors can be swapped but is the left rear knuckle the one that reads speed?
 

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Discussion Starter #7
OMG - an Anthracite apart like that! - Is nothing sacred? Blasphemy! ;(
lol, what do you mean? Referring to m maintenance thread from the summer?
 

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Discussion Starter #8
Sorry to be a little off topic. I know the sensors can be swapped but is the left rear knuckle the one that reads speed?
Yeah, maybe it wasn't clearly spelled out in my post, but yes the left rear is the sensor that gives the input to the speedometer. I don't know why they don't have it cross referencing with another wheel so if the left rear sensor dies the speedometer would still work. Seems like a redundancy that BMW would have thought of!
 

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Discussion Starter #9
Unless I get other feedback, my plan will be to replace my axles this weekend and double check the wheel bearing mount bolts, etc. Hopefully I don't ruin a bearing while trying to push the axles out. For reinstalling, looks like Timmay used the reversed nut just for getting it threaded and then pulled it in with homemade tool... why can't I weld a big nut on the collar side of an old axle nut for sucking the new axle in so I don't damage the new ones like I did to these? Or won't I be able to drive the nut on like that without damaging the hub?

Once this job is done and I don't find anything after checking the torque on the bearing bolts, I guess I'll have to buy another sensor, but what would cause the right side to rub? I'll be looking at that when I have the axles out.
 

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Getting the axles out is the tricky part, getting them on much less. Welding a nut to the old axle nut can work as can flipping the old nut - drawing the axle on using a nut is the way to go.

As to why the sensor is rubbing :dunno: The tone wheel is integral to the bearing and obviously the sensor should not be contacting anything, but you won't know until you get in there and even then it might not be obvious.

Did you buy the OE bearings at a discount? :rofl:

It is very typical for the manufacturers to use only one wheel speed sensor for the speedometer.
 

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Discussion Starter #11
I'm not too worried about getting the axles pressed out since I just did it 4 months ago. Hopefully they're not seized yet.

The bearings were the "value line" kit from BMW. ouich Besides the good price ($100 per), I got the kit because it came with all new bolts and nuts. :dunno:

I'll probably experiment once the axles are out and there is more room to see things. I'll put the non ground down sensor in that hole and see if it still rubs or maybe some crap got suck in there and caused the wear. Not sure.
 

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With that left wheel speed sensor code, you need to change the sensor. It sounds like you are planning to do that. The trifecta lights coming on and the speedo failing while you were stationary means the sensor internal circuit is failing randomly and intermittently and the module, which constantly monitors it, is immediately shutting things down.

And as rao says, the rub on that sensor does not bode well for the quality construction of the bearing. If you have dial calipers, compare the depth of the toothed ring in each hole.
 

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Just wondering if you have done the diode test for the sensors?

Another possibility is the ABS module. I think intermittent faults are often caused by a solder joint in it.
 

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I would put my vote on the ABS module. I am experiencing the same issue now and will soon send mine out for repair. From other forums, I have seen a few other E39 models complaining out the same issue and then seeing a fix once the ABS module is repaired. Keep us updated and I will follow up with results on mine once I get it repaired
 

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Discussion Starter #16
so what is the final diagnosis after this weekend's work?
Nothing is final when dealing with such a sophisticated automobile.
 

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Discussion Starter #17
I would put my vote on the ABS module. I am experiencing the same issue now and will soon send mine out for repair. From other forums, I have seen a few other E39 models complaining out the same issue and then seeing a fix once the ABS module is repaired. Keep us updated and I will follow up with results on mine once I get it repaired
After doing some work this weekend and having the issue come back today, I'm lead to think you are correct.

Among the work of replacing both rear axles due to failed CV boot cups I swapped the rear ABS sensors side to side. While everything was apart I cleaned the tone wheel on both bearings and inspected for damage. Still not sure how the one sensor got worn into, but it's not the cause of my problem.

Today I had to make an hour drive to a jobsite for work. During the drive the problem came back, same as usual. So this rules out the sensor for sure, and since the code is for a circuit failure, it makes me think the problem is still in that wheel sensor circuit. That points, as mentioned above, to the ABS module. I've removed the connector in the past and added a bit of dielectric grease and inspected for corrosion, finding none at that time.

Are there any tests I can run to confirm? I'm thinking not since this is an intermittent problem. I'll probably have to bite the bullet and get a new module? (used) I can't afford to have the car down long enough to send mine out for a rebuild. I have GT1/DIS for coding in the module so no issue there.
 

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Are there any tests I can run to confirm? I'm thinking not since this is an intermittent problem. I'll probably have to bite the bullet and get a new module? (used) I can't afford to have the car down long enough to send mine out for a rebuild. I have GT1/DIS for coding in the module so no issue there.
According to link below, people have driven the car without the module in place.
abs traction control, speedometer not working - Bimmerfest - BMW Forums

The following are typical of not having it in while getting repaired:

BTW, while your ABS control module is out of the car (about 5 days), the following anomalies may occur:
- Brake/DSC/ABS trifecta solid yellow lights (on the instrument cluster)
- Service Engine Soon (SES) solid yellow light lit (on the instrument cluster)
- No ABS (upon hard braking under low-traction conditions)
- No traction control (DSC or ASC on lateral action)
- No speedometer (use a portable GPS navigation unit if you're worried about that)
- No odometer (again, use a portable GPS unit if this bothers you)
- No tripmeter (use a portable GPS unit if it's a worry to you)
- No cruise control
- OBDII diagnostic trouble code DTC P0500, i.e., bad speed sensor (clear by driving or with an OBDII scanner)
- No possibility of passing (California at least) smog inspections (until you replace the ABS control module & clear the DTC)
- No speed-sensitive automatic door locks (if enabled at the stealer)
- No GPS (if you have navigation)
- No mileage calculations on the instrument cluster
- No fuel consumption calculations on the instrument cluster
- No range indications on the instrument cluster
- No speed-sensitive radio (if equipped)
- No speed-sensitive wipers (if equipped)
- Erratic fuel gauge (especially when near empty, so keep the tank at greater than 3/4 at all times)
- Erratic transmission shifting (if automatic; if it bothers you, switch to manual shifting)

If you are smarter than me, you can follow these directions to test the circuits. I really don't want to bother with it since I don't have the time right now and have, like you, swapped left and right sensors only to find the same problem. Bimmerfest - BMW Forums - View Single Post - 2002 E39 ASC BRAKE ABS lights on => Diagnostic Procedure & Parts Location

Lastly, if you choose to use BBA for repair, the best deals look like they are on their ebay page as opposed to their direct webpage. I believe this to be the correct link but make sure before you purchase: BMW Bosch 5 7 ABS Module Repair Service | eBay
 
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After doing some work this weekend and having the issue come back today, I'm lead to think you are correct.

Among the work of replacing both rear axles due to failed CV boot cups I swapped the rear ABS sensors side to side. While everything was apart I cleaned the tone wheel on both bearings and inspected for damage. Still not sure how the one sensor got worn into, but it's not the cause of my problem.

Today I had to make an hour drive to a jobsite for work. During the drive the problem came back, same as usual. So this rules out the sensor for sure, and since the code is for a circuit failure, it makes me think the problem is still in that wheel sensor circuit. That points, as mentioned above, to the ABS module. I've removed the connector in the past and added a bit of dielectric grease and inspected for corrosion, finding none at that time.

Are there any tests I can run to confirm? I'm thinking not since this is an intermittent problem. I'll probably have to bite the bullet and get a new module? (used) I can't afford to have the car down long enough to send mine out for a rebuild. I have GT1/DIS for coding in the module so no issue there.


Take a look here:

ABS Module Repair Info for E39 (from Volvo forum) - Bimmerfest - BMW Forums

http://www.m5board.com/vbulletin/e3...-dsc-abs-module-re-solder-assy-terminals.html

Regards,
Jerry
 

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