FAQ - Traction Control Errors / Random braking / Instability Problems / ABS & DTC Issues

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marco_polo
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FAQ - Traction Control Errors / Random braking / Instability Problems / ABS & DTC Issues

Post by marco_polo » Sun Oct 15, 2017 5:04 pm

The issue: Traction Control Errors / Random braking / Instability Problems / ABS & DTC Issues. Symptoms commonly starts as TC intervention during left or right hand bends, then on straights, then near constantly.

Diagnosis: Turn all your traction control nannies off my holding the DTC button for around 5 seconds, then re-test your car carefully. We don't advise trying this test in slippery/dangerous conditions for obvious reasons! If they're bad enough, they may also throw a 'Wheel speed sensor rear extrapolation' error. You can also check the wheel speed sensors via live monitoring of the wheel speed sensor outputs using a laptop and BMW software or similar.

The usual cause: Rusty rear driveshafts. The driveshafts corrode, and the rust causes the Reluctor/s ring to expand, and sometimes crack too. If the ring expands enough, it will make contact with the wheel speed (ABS) sensor. Here's a good photo courtesy of Teasdas:

Image

Solution: Basically you need a new reluctor ring, and quite possibly a new ABS sensors too. No coding required. Reluctor rings are available from eBay for around £5.

Image

Method (courtesy of dozydoog):

The hub nut (Number 4 in the image below) should not be an issue, it' simply a 30mm or 32mm socket job but the nut is staked to the grooves in the end of the drive shaft, these need knocking out before you wind the nut off to avoid thread damage. Breaker bar makes easy work of the factory 190nm if someone applies footbrake with engine running

The splines will be tight, wind nut off about 3mm then find a bar that fits inside the nut and apply a solid whack with a lump hammer. please dont hit the nut or the driveshaft end with the nut removed, you will cause damage, mine went with the first solid blow. needs a new nut on re-assembly. If it's really stuck, soak with 'Plus Gas', leave overnight and retry in the morning. Never be tempted to strike the end of the M24 shaft, you'll peen it over and wreck the thread. If you have to, use a plastic / hide or other soft hammer.

Once the drive shaft has moved tighten it back into original position but only to low torque

Image

To split the driveshaft, the 6 drive shaft to axle torx bolts (Numbered 3 in the image above) have to be removed with care, do not damage the inner cv joint gaitors. You will need a assistant to lock the wheel in various position with a bar placed across 2 replaced wheel studs as you need to rotate the shaft to get at each bolt in turn.

Shaft should now compress and clear the diff casing. The issue is on the nearside where rear 2 exhaust mounts need to be eased off to allow the shaft to clear the diff, once done the shaft can be knocked from the hub a 2nd time, much easier.

Ok, on mine the amount of rust under the ring had expaned it by at least 1mm. quick crack cross the ring with a chisel and it's off.
by the time the rust was chipped off, ire brushed, filed off and emery'd i'd guess there was .25mm clearance with the new , we had to use epoxy as loctite would not have done.

reverse for putting back together, but again, mind the drive shaft gaitors. getting enough thread showing through the hub to engage the nut will be a problem, ensure everything is cleaned and lightly oiled then tap with a soft hammer on the inner face of the drive shaft until the threads can be accessed.

E Driveshaft male torx bolts vary with car model:
M8 bolts - 52Nm
M10 bolts - 80Nm

(drivers side is much simpler due to no exhaust)

Whole job about 1 1/2 hours for an old git like me and in total for both sides was £13, £4 each reluctor ring and £5 for the epoxy as had run out.

An alternative to glue-on rings are the heat-on variety, see here for a turotial:



It's good practice to replace the 6 driveshaft bolts and hub nut, parts available from Cotswold BMW or your local friendly parts counter. Just give them the last 7 digits of your VIN to ensure you get the correct parts for your car.

Alternative fixes: If you don't fancy gluing a new ring on to your old shaft, you can buy a replacement pattern drive-shaft for around £100 from various motor-factors.

Disclaimer: This FAQ post is intended to be as balanced and accurate as possible, but this thread should be considered as opinion only. We can not be held responsible for injury, damage or expense caused.
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