Electrical issues.

[JamieIsf]

Good Afternoon All,

Apologies if any of you have read this on the Facebook group, but I am now baffled with the issues of my beloved Z4.
Yes, I'll hold my hands up to start, I did not look after it too well over the winter - did not leave on charge.

Went to start for first time in couple of months and it did not start. I have outlined our trail of progress over the weekend:

• Went to start car first time since beginning of Jan 24
• Would not start. No sign of life, had to unlock with key.
• When plugged into charger, battery read 1.4v, and would no charge.
• Jump start using terminals under bonnet, car started, left to run, battery would now charge left over night to +12v.
• Car started next morning, however, pressing brake increased the revs on the car, no radio, no roof function, indicator/hazards worked, but not showing on instrument cluster. Windscreen jets do not run, central locking button no work. Airbag light on.
• Brake lights also stay on c.2 minutes after removing key from dash.
• Took for a drive of c. 20 miles, car running fine mechanically until 3 lights on dash to suggest ABS warning – probably unrelated/ maybe to do with low charge. Have photo of lights on.
• Got back home, and decided to take battery out whilst changing oil, charging ok, and showing a ready of c.13v.
• Tested roof motor to see if receiving voltage and nothing. Checked fuseboard, all ok and receiving power.
• Left overnight, and took for 30+ mile drive today. Pre starting car, ready voltage of 11.5v
• Ran an Autel scan to identify and potential issues. Fault codes as below.
3.1 87 KOMBI: K bus
3.2 BE KOMBI: Data-filing difference to central light module

• Identified that it was under fusebox and noticed car wet in that area, but doesn’t seem to have affected any wiring or terminals.
• Decided to check radio if receiving power, which was, yet not working, but oddly cd drive works when no power to car – yet doesn’t work when power on.
• Then considered Airbag control module – slight corrosion on live terminal, but all ok and receiving power.

I'm totally lost now - i suspect i will now need to take to a specialist who can communicate properly with the car.

Would add it drives beautifully, i don't feel as though there is a transport mode on.

We're now reading about the GM5 module - would this be related?

Any thoughts would be massively appreciated, as at a total loss.

[Usel]

Unless you know somewhere to take the battery to have the capacity tested then I would pop a new battery in the car first.

Even though the battery reads 13+ volts and can start the car it doesn't mean there is much capacity there.

If the GM5 has been getting wet or a source of damp near it then corrosion inside could be taking place. Its relatively easy to remove it and open up the casing to have a look inside at the circuit board.

[j3nks79]

I’d start by replacing the battery. Then test the alternator to see if it’s putting out 14.1v when idle.

[enuff_zed]

If the battery got that low there's very little chance it's still ok tbh.
You can chase all the different codes etc, but until you are 100% sure the battery is good you are never quite going to know if you are fixing a problem or a symptom.

With the greatest of respect, you are reading a lot of scaremongering stuff with little personal knowledge as far as I can ascertain.
I've also noted that the fb gang are throwing in a lot of unfounded hearsay. From experience I would suggest that this forum is going to be a lot more focused and a lot less 'my mate said it could be that'.

Don't take this as criticism please.
Get a new battery, clear the codes and see what comes back.
At the same time, work out why the car is wet inside and cure that. If it's up behind the fusebox then get the scuttle panel off and clear out all the vents. Could be water building up and getting in round the pollen filter housing.

The K-Bus is like a ring main between all the modules. If one of those has an issue it can confuse all the other modules. Find the faulty one and it cures all the other symptoms too.
The centre airbag module SIM85 is the favourite culprit. Just because it is receiving power doesn't mean it is working inside. If a terminal is corroded, the 12v arriving at the plug may not all be getting past that dodgy pin.

So:
1. Fit a new battery and clear all the codes
2. Find where damp is getting in and fix that
3. See what codes come back
4. Come back to us and let us know what issues are still there
5. BE PATIENT! Don't start diving in. Do one thing at a time, reset and see what is left.

[JamieIsf]

Dear All,

Thank you for your help, it's truly appreciated.

enuff_zed '

with little personal knowledge as far as I can ascertain.

' I take great offence... No I'm joking you've hit the nail on the head, I'm fairly handy with a socket set and can service and run basic maintenance, but electrics, I've no idea - all i can do is test and check to see if voltage is getting to the units/ earthing correctly etc. I haven't done anymore work than I wanted to anyway, as the interior has a nasty wrap i wanted to get rid of anyway, so stripping the interior was always part of the plan!

I think the first port of call is the battery, I'll check the voltage tonight and see if massively dropped - it is only a year old so hopefully get replaced under guarantee.
Would be very handy to try with another battery, i have a Land Rover too, but will have to check to see if that battery is compatible.

I'll keep you updated. J.

[JamieIsf]

Dear All,

An update. You may all well be correct, I have just returned from a Business trip for 3 days to find the car totally dead.
Either battery is not holding charge, or something is draining the battery usage (although would it drain that quick?), I suspect the former.

[enuff_zed]

Dear All,

An update. You may all well be correct, I have just returned from a Business trip for 3 days to find the car totally dead.
Either battery is not holding charge, or something is draining the battery usage (although would it drain that quick?), I suspect the former.

Check the light in the storage compartment between the seats is going off.

[coldel]

Its pretty well documented on here that even a battery that is having a little wobble with itself can throw all sorts of random lights and codes on the E85. It was the first thing I bought when I bought my E85 last year even though I wasn't getting codes or lights, brand spanking new Yuasa.

And agree with above, FB is full of utter nonsense a lot of the time and many threads end up with people who answer arguing pointless semantics with each other in some sort of effort to 'win' rather than actually helping the OP.

[colb]

Agree the Facebook Z site is full of people just making wild guesses about problems people have. Far better to come to this Forum for sensible explanations and advice.

[raymond.harper]

I am in Ringles Cross Uckfield Jamie. In my glove box is an Ancell BM700, if you ever want to borrow it you are more than welcome.

[Rockhopper]

I'm one of those Facebook group "know it all's"!! I told you ages ago to get a new battery then see what happens

[Big Bad Boris]

Best advice here is to heed Enuff Zeds advice. He’s fixed more these of than I’ve had hot dinners…. and I like my grub

[JamieIsf]

Thanks All,

Lesson learnt, I'll come straight here next time - pure laziness, in posting on Facebook rather than taking time to post on the knowledgeable forum.

Raymond - good to e-meet you. I've got an Autel AP200 which I've been using on my Land Rover (don't get me started on that) but i'll drop you a message.

Half day tomorrow - hopefully have an answer by tomorrow/end of week/ when the bloody sun comes out!

[JamieIsf]

Today's update.

Not the battery i have a new one plugged in.
Still doing the same weird things revs when applying brake on startup, hardly and components work etc.

I found a couple of video's/ websites about the Red/Yellow/White block in the Kbus, and if showing low voltage that could be an issue, but all showing 11.5v+

Wondering if it's the actual GM5 module now, and if that's gone bad. Is there a way to test this?

[enuff_zed]

Today's update.

Not the battery i have a new one plugged in.
Still doing the same weird things revs when applying brake on startup, hardly and components work etc.

I found a couple of video's/ websites about the Red/Yellow/White block in the Kbus, and if showing low voltage that could be an issue, but all showing 11.5v+

Wondering if it's the actual GM5 module now, and if that's gone bad. Is there a way to test this?

Some of the stuff you mentioned isn't through the GM5 though.

The revs rising when you brake could be a separate issue. Often an air leak affecting the servo vacuum supply. Check all the pipes under the bonnet.
A couple of times I've witnessed the same set of symptoms and they have been due to one of the modules on the K-Bus being faulty. On the first one it was the central airbag module (SIM85) under the coin holder behind the handbrake. Something had been spilt on it and the plug was full of crap and corroded. Had to change the module.
Second time, someone reported same issues as you on the forum. I mentioned the SIM85. He pulled the plug off, cleaned it up and luckily for him it fixed it.
If you lift out the coin tray and have small hands you can get to the plug. It is a lever type, hidden behind the big green plug with the optical cables in.