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Discussion Starter #1
Hello esteemed folks.
After a long period with no issues , my 840Ci hit back with an odd few issues. Having replaced capacitors in the GM2 made no difference whatsoever..hence the post.
Symptoms:
Following a night of torrential rain , I went to unlock the car.
Unlocking either door, popped the boot open. In other words central locking worked and unlocked doors and opened boot.
Trying to lock / unlock again revealed central locking stopped working.
With boot open pushing the boot release does nothing.
Windows work sporadically, and as it happens only go down when they do!
Wipers stopped working.
Interior lights work fine.
When removing the GM2 to repair (urm..batteries were connected) wipers worked. But..that was only once.
All capacitors replaced , put back in and problem is unchanged.

While I wait to take her to be scanned (money ultra tight lately) can anyone share their opinion if it could be bad grounds or anything other than the GM ?
Reading the diagrams does point to either an RM or GM problem but no longer sure.
Hoping to spend time in the boot , but fear it was never the GM to begin with...

Would appreciate any opinion except the completely useless ones :)

Thanks for reading the post and for any feedback!
Nik aka Bubble
 

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It could just as easily be the relay module (alongside the sill by the passenger seat). They are about as reliable as the GM. I would start with some checks around there - make sure it has decent power etc. There's a ground point in the passenger footwell worth a check for corrosion etc.
 

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Discussion Starter #3
You might be hitting the nail on the head; I did have a sunroof leak on the driver side..so definitely worth a check.

We talking passenger side in left or right hand drive side?

Thanks purpleblob, shall report later!
 

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In right hand drive cars it's on the left. I'm guessing it's the same place on left hand drive but I don't know for certain. I'll check the ETM when I get in front of a proper computer

EDIT:
"Inside box on interior side of LH door sill" is all it says. So I assume it's there for all variations.
 

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Discussion Starter #5
Spot on, I dug up the diagram and thought if module is on the LHS so will be this.
Now...when I got it out , was shocked.
The pics say it all. Found a 2nd hand one which despite not being an electronics engineer.......pretty sure the board spent a lot of time underwater.

At least looking at capacitors crumbling understand where the gremlins came from!
 

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Discussion Starter #8
Thank You - there are two so will be ordering one today. One question I do have , relating to a long standing ASC and ABS lights permanently lit on the dash:

What are the chances water made it into that causing the lights to be permanently lit?
Is the asc box easy to open and examine like the other modules?

Cheers folks! Hoping I can gove back to the group one day!!

Must admit I lose interest in my E31..seem to have had a myriad of problems due to non driving her often :(
 

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You'd be better getting the codes read in the first instance for that one.

The modules up behind the dash somewhere - not one I've ever had to take out (yet!)
 

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The modules up behind the dash somewhere - not one I've ever had to take out (yet!)

The ABS/ASC module is on the near side (passenger side on a RHD car) door sill under the carpet

It can be accessed "just" without removing the seat (you'll want to move it as far back as poss)

Held in with 3 or 4 10mm headed set screws. One large multiplug with lots of wires .....

As PB says, before doing anything get the codes read. You really don't want to mess with the ECU only to find it is a wheel sensor

The ECU is different for each of the engines i.e. the ECU from a 4.4 will not work with a 4.0 or a v12 and vice versa

The ECU box is riveted together discouraging you from opening it up and apart from being able to visually inspect and on seeing fried circuits or corrosion and confirming "yup it's bu**ered" I'm not sure what mileage there is in opening it.

If you have a v12 I actually have an ABS module in the garage (bought via eBay before I realized they were different - D'oh!) you are welcome to it, if you have a 4.4 I can tell you that BMW have got them in stock at about £700 - gulp!! I managed to find one from a crashed car in a scrapyard when Sue's went wrong - phew.

Hope this helps

John
 

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Discussion Starter #11
Thanks. Yep found the riveted module next to the RM and as my RM had been immersed...
The problem was always (and maybe should have worked this out) reading the errors returned a fault , clearly as the BUS could not run through the fried board. I have an M60 4.0 but will do thr RM first and move to the next fissue.

Being made redundant this week left me thinking at least now I have time to fix all these things , although as part of buttoning down the hatches she might need to go :(
Thanks friends , will report once the RM is in.
Cheers!
 
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