What I did when the ABS light came on

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hobbers
Joined: Sat 03 Jul, 2010 16:58
Posts: 6

  Z3 roadster 2.8

What I did when the ABS light came on

Post by hobbers »

Today I got my 1999 2.8 Z3 back on the road for this season. Yippee - roof down at last! But I had some issues to resolve before I could MOT and tax it. I use various forums for clues to help me move forward with problems and realise that I rarely give back. Today I want to correct that and add what I hope is useful nugget for my fellow zedders! So the story begins...

As you have gathered this issue is what I did when the ABS/DSC light came on. What next? And perhaps more importantly, realising that you lose these features when driving. Easy to forget and no good remembering when the backend goes out of control.

Fault Finding
So, with my Maxiscan MS509 OBDC it told me I had a P0500 fault. Wheel speed sensor. But know idea which one. So I changed them all and checked the cog-like wheel that fits on the wheels hubs. If your vehicle has ABS fitted it has to work for the MOT ticket.
The front sensors we're seized in and had to be pin-punched out. Heating might have worked but didn't try this as was replacing them all. The rears not so bad and did eventually come out. I'm of the opinion that if I replace one I replace them all. Got the fronts off ebay and the rears from Euro Car Parts. All for about £170. Quite expensive for four coils!

So they were replaced and...... no change. ABS light still on.

After some research my OBDC Tool was inadequate. It just looks at the codes for the ECU. What I needed was a tool that could read the beemers ABS unit. What I then bought was the highly recommended BMW & Mini C110 Diagnostic Code Reader 1997-2011 models - Airbag, ABS, Engine & Transmission from http://www.bavariandominator.com for around £80 quid I think. No, I'm not getting any commission! Interesting to note that I had to use the D100 connection under the hood (located just above the ABS unit) rather than the connector above the brake pedal to get the ABS readings. Luckily the C110 also come with the adapter and case.

So now I got much better info. Wanted to upload an image here, but the forum won't let me :(

In the chassis settings, I got a code 41 Speed Sensor rear right and code 71 ABS pump fault. Also found Airbag sensor fault and Exhaust camshaft sendor fault. But thats another story.

Finally getting somewhere. I re-seated all the sensor connections and set to working out how to fix the real issue of the ABS failure. I didn't want to just remove the unit without a reconditioned replacement.

Finding a Replacement
On my Z3 the unit has the control unit/hydraulics/pump motor in one unit, located on the right-hand side facing into the engine compartment (in the vicinity of the fuse box). The part number is 34.51.1.164.898. I did some googling and found a breakers site with a unit available for £50. Remember that a brand new unit from BMW is going to set you back over a grand.
But I had no idea what the condition of the unit was in. Yes I could have fitted it and sucked-and-see. Not wanting to go out in the cold unnecessarily, and preferring to fit a re-conditioned unit, instead I found http://www.autotekelectronics.com based in Dorset who specialise in all things ABS. After a helpful phone call, I sent the unit to be tested for £50. Not good news the unit had an ECU fault. I parted with another £200 quid and it came back reconditioned, tested and with a 3 month guarantee. It looked almost brand new. I could now replace the unit in the knowledge it would actually fix the problem.

Replacing the unit
Actually, a lot more straightforward than I thought.
1. Buy some replacement DOT 4 or 5 brake fluid. I eventually got through a litre. Maybe buy an automotive syringe.
2. Remove the air-intake box, pipe (jubilee clips) and disconnect the Mass-Airflow sensor.
3. With a syringe, drain off the brake/clutch master cylinder as much as you can.
4. Disconnect the 6 brake pipes from the hydraulic unit. The feed in will still leak - got a cloth under the car if wife fussy about how the drive looks:) Make sure you have a decent fitting spanner or open ring - 11mm if recall correctly. A couple of the pipe nuts where tight and would be easy to round off.
5. Unscrew the securing bolts from bracket - sort of hidden from of view a bit.
6. The unit has two stubs that fit into rubber mountings on the wheel arch bit.
7. Reverse steps 6 to 1 with the new unit and job done.

Bleeding the brakes
With the unit replaced you will have to bleed all the brakes starting with the rear offside, the rear nearside, front offside and finishing with the front near-side.
When I first attempted this, I had mostly travel in the brake pedal and couldn't resolve. So not too successful.
I got a useful tip from a mechanic friend and was to do it all again with the engine running - presumably to get the vacuum assistance. Worked a treat. Loads of air coming out of the rear calipers. Beemer manual says open the nipple, 10 pumps and hold down the pedal and lock off the nipple. Brake feel now returned when all four done.

Did this fix work?
Bloomin right! once I used my dead handy C110 to reset the ABS codes. Amazing, the lights went out and stayed out. And once I resolved the Airbag light (another story) my dash is clear of faults. And is still that way today!
When I got the car MOT'ed and took it out for a proper test, I could throw the car around corners and the DSC light flickered on (prevent wheel spin). And then went out again :) Haven't been in the rain yet to do a true ABS test but confident it will work. And yes the ABS/DSC button turns the feature off and on once more.

Summary
Well, this little project has set me back a spare bob or two. I think if there is any advice I could give it is to get a C110 first. I could potentially have saved about £120 on sensors and sent my own ABS unit of for repair, saving another £50. But you know, I have the original unit to send of for repair and could easily get my money back on eBay (take a look). But will keep it as a spare I think. And now the wheel sensors are replaced, its once less thing to think about in the pursuit of keeping me zed alive!

Hope someone else finds this useful.
1999 Z3 Roadster 2.8 M52 TU Twin Vanos Manual in Cosmos Black
John Wilson
Joined: Fri 12 Jun, 2009 12:11
Posts: 252

  Z3 roadster 2.0
Location: Diss

Re: What I did when the ABS light came on

Post by John Wilson »

Great account. This sort of sharing is what I most like about the zroadster site. Thanks.
Alan W
Joined: Thu 20 Jun, 2013 10:56
Posts: 670

  Z3 roadster 2.8
Location: Bexley, Kent UK

Re: What I did when the ABS light came on

Post by Alan W »

Great post, thanks for that
1999 facelit Z3 Roadster 2.8 Auto in Cosmos Black aka 'Gloria'
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bertiejaffa
Joined: Fri 26 Jul, 2013 09:28
Posts: 1733

  M roadster S50
Location: Manchester

Re: What I did when the ABS light came on

Post by bertiejaffa »

great write up - the unit on my 2.0l needs reconditioning too. Interesting that you were able to get one off ebay and fit it with no issues, I know a few people who have struggled with getting the donor unit remapped to the car - looks like you managed to get a unit off a car that was a perfect donor for your model
Here come the girls.....
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My //M Refurb
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hobbers
Joined: Sat 03 Jul, 2010 16:58
Posts: 6

  Z3 roadster 2.8

Re: What I did when the ABS light came on

Post by hobbers »

Hi Bertie - I had read similar accounts but made sure I got the exact part number. This limits the choice available but hopefully doesn't add more problems. It might also be that the reconditioning has reset the unit in some way. Speculation on my part though.

Thanks to all for the feedback
1999 Z3 Roadster 2.8 M52 TU Twin Vanos Manual in Cosmos Black
Zed Carer
Joined: Thu 13 Dec, 2007 20:27
Posts: 1642

  Z3 roadster 2.8
Location: Wakefield

Re: What I did when the ABS light came on

Post by Zed Carer »

hobbers wrote:Hi Bertie - I had read similar accounts but made sure I got the exact part number. This limits the choice available but hopefully doesn't add more problems. It might also be that the reconditioning has reset the unit in some way. Speculation on my part though.

Thanks to all for the feedback
If you can get the same part number from an identical vehicle; i.e. another 2.8 Z3 then there is a good chance that no re-coding will be required. When I fitted my 2nd hand replacement unit Details Here the ABS light automatically reset itself and went out straight away. The problem is the ASC (or DSC) controller that is coded to the car and, although the unit had the correct part numbers (ABS pump and ASC controller) it was from a 2000 E46. I got mine re-coded at Quarry Motors in Sheffield and was told that anyone competent with INPA could do it using Coding Expert. If you get an existing unit refurbished then it will be coded as part of the process. I've still got my old faulty unit in case the one now fitted goes wrong but it is a bit hit and miss as 99% of the time it is just dry solder joints in the ASC/DSC controller.
Hers: Z4 2.0i Sp --------------------- His: Z3 2.8
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