E85 will not start - multiple problems or just one?

AndyOn4Wheels

AndyOn4Wheels

Member
 Cambridge
I have a 2004 registered BMW Z4 E85 3.0i SE (57,000 miles) that won’t start. It started and drove perfectly for months. Last week I put it in for its MOT, drove it home without issue and the following day it wouldn’t start. I haven’t been able to start it since. Using a Foxwell NT530 code reader I identified a fault code 281C (DME: Bit-serial data interface (BSD): signal). I’d be grateful for any advice on the probable cause and how to fix it.

It’s worth adding that the airbag warning light has been showing for 2-3 months. Automatic scanning results have consistently returned faults for the KOMB (instrument cluster) and SBSR (Satellite, B-pillar, right). I can clear the KOMB fault but not the SBSR.

The following may also be significant: when the car first wouldn’t start I assumed that the battery was flat (because there was a click) and foolishly attached my NOCO Genius 5 charger to the battery terminals directly. I have since read that this was not a good thing to do.

I have explored the following:
  • Battery: Interestingly, I think the battery may have been flat – or at least low in charge – during my first failed attempt to start the engine. Once it had a ‘full charge’ it retained it – sort of. It went from 12.47V (which I know is low for a full charge) to 12.38V overnight, which probably indicates that the battery may be on its way out. I tried jump starting it (using the correct terminals under the bonnet this time) and got a reading of 14.5V while connected. But it still wouldn't start.
  • Ground straps: Can’t get easy access but I used a jumper cable to ground it, and it made no difference.
  • Alternator: I disconnected the small wire at the back and attempted to start the car, but still no joy.
What it could be:
  • IBS: Now this is where I could use some help. Is this model fitted with IBS? There appears to be some debate. And what is this black plastic ‘wheel’ fitted to the negative battery terminal, please? (See picture) It screws in and out. When screwed in there is a sound that seems to indicate that it has engaged something, but I’ve found no pictures of anything that looks similar on the forums etc.
  • Wiring harness: I’ve read that I should ‘inspect the BSD communication wire connecting the alternator to the DME for corrosion and damage’. While I’ve visually checked both wires coming from the alternator, their full length is hidden, and I don’t know how to go about checking them with a multi-meter.
  • Voltage regulator: How can I check whether it’s this or the whole alternator that needs replacing?
  • Alternator: As above. And what is the difference between a £150 alternator and a £350 unit, please – apart from the cost, obviously?
  • Starter motor? Would it go without warning, though?
Any guidance grateful received.

PS I’m only able to check in periodically, so please forgive me if I don’t respond promptly.
 

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Starter motor

Especially if it’s been stood

Easy way to rule it out is get a long bar and hammer, give it a damn good whack

If it starts then it’s that

I think your DME code is signal generated issue so that shouldn’t be a non start issue. Same applies for your airbag SBSL issue.
 
Hi. I’m in Norfolk so not too far away. The wheel on the negative terminal is an aftermarket device to disconnect the battery. I would get rid of that first!
The voltage regulator is easily changed in situ. I’ve done a few.
I am also fairly proficient at fixing airbag snags.
As the car won’t start, I could perhaps come to you to see what we can work out?
 
As @bigwinn says, the starter motor is the possible culprit.
Easy to change without much hassle. Again, I’ve done a few and happy to help out if needed.
 
Can you hear the starter clunking? That eliminates EWS/wiring etc. At this age starter solenoids tend to get sticky and don't travel far enough to engage fully. This gets worse with sitting. Remove starter, remove solenoid, clean plunger and give it a wipe of WD40 and reassemble.
 
My starter went a couple years ago out of the blue with almost no warning. It was a little slow to start two times I started it, and then the third it clicked and did nothing. I also thought it was the battery at first and replaced it, and it started once but then didn't start again. Replacing the starter solved the problem immediately. Mine was 22 years old with 70k on it, so about the same as yours is now.
 
As mentioned already, I think the first thing I'd do is to remove the aftermarket isolater gubbins on the -ve terminal - it's almost certainly not the culprit, but eliminating it can't hurt.

(Just to add to this, one of my rules when it comes to anything engineering-y is that what isn't there can't weigh anything and can't fail. This sounds like a very Colin Chapman kind of philosophy, but I don't think it's one of his quotes).
 
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Oh, and I'm pretty near Cambridge too - so if you need a hand, give me a shout. I'm not an expert, but I can happily sympathise and drink tea while trying to work out who we should ask next.
 
This forum never ceases to impress me. Thank you all for your advice. It seems clear that the consensus view is that it's the start motor - which is reassuringly simple and well within my capabilities! Thanks also for the guidance on the aftermarket isolator gubbins. I'm interpreting that as meaning that it isn't the fabled IBS (which I'm now reassured isn't fitted to this model). I really appreciate the offers of direct help (and tea and sympathy), but I'm probably(!) able to take it from here alone. Of course, if either a decent whack or a replacement/repaired starter motor don't do the trick I'll be back again for more advice! ;-) Last question, is there a definitive post on the well-known airbag light issue? That will be my next challenge. Thanks again.
 
AndyOn4Wheels said:
is there a definitive post on the well-known airbag light issue? That will be my next challenge. Thanks again.
Click to expand...
Not one single post, but if you search for posts by me (or ones I've answered) you'll find plenty of info on it all.
Do note that not all modules are compatible, so if you can find the part number of yours and post it up, we can give you the full list of ones to look for. It'll be a 7 digit number starting 69_____
 
enuff_zed said:
Not one single post, but if you search for posts by me (or ones I've answered) you'll find plenty of info on it all.
Do note that not all modules are compatible, so if you can find the part number of yours and post it up, we can give you the full list of ones to look for. It'll be a 7 digit number starting 69_____
Click to expand...
Forgive me if this is a stupid question, but where can I locate my module part number?
 
AndyOn4Wheels said:
Forgive me if this is a stupid question, but where can I locate my module part number?
Click to expand...
No such thing as a stupid question, but loads of stupid answers out there!!

The SBSR is located behind the drivers seat, mounted vertically on the rear of the inner sill. A square metal box about 10x10cm. It has two plugs, black electrical and green fibreoptic. The part number is on the top right corner of the label.
However, a lot of scanners can give you version info, which may well show it without having to pull up the carpet.
 
BTW, I've seen a lot of cars with the 281C (DME: Bit-serial data interface (BSD): signal) code and it's often only come to light when looking for something else. It doesn't seem to have any great effect if I'm honest. Possibly means it has an aftermarket alternator or voltage regulator fitted.
 
The airbag and an odd 'clunk' when the hood reaches a certain point when retracting. I'm pretty sure I read a thread on that here, though. On which subject: I really need to get around to resiting the roof motor too!
 
If you need to read codes from the airbags, I've just ordered an Autophix 7910 - I saw just how quickly and easily @enuff_zed scanned and reset mine at the weekend using one, so it was a simple choice to pick one up. Should be arriving later this week, and I'm only just up the road from Cambridge.
 
enuff_zed said:
Not one single post, but if you search for posts by me (or ones I've answered) you'll find plenty of info on it all.
Do note that not all modules are compatible, so if you can find the part number of yours and post it up, we can give you the full list of ones to look for. It'll be a 7 digit number starting 69_____
Click to expand...
Couldn't locate the physical module, but my scanner was able to supply the following: BMW part no 6942102, coding index 4, date of manufacture 14.10.2003, diagnosis index 2656, hardware number 03, supplier Autoliv, physical hardware no 6936186, trouble code 98CA not present.
I'm curious: what's the difference between the 'BMW part number' and the 'physical hardware number'?
Apologies for treating you like the font of all knowledge, but you've clearly walked this path before! :cool:
 
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