Electrical gremlins in my e39 - PLEASE HELP!

[535iase1997 2]

Hi all,

I know it is VERY common for an E39 to have some electrical problems, but I have quite a few.

What I will start with is - No communication with any modules, I have even had it at Jeff Gray for a few hours, with no success.

This is my second E39 V8 and I enjoy working on them, but this one has me stumped.

The reasons why I want to read the fault codes are as follows:

* I have the stability control light up (most of the time)

* ABS light comes on momentarily every time I start the car, after about 50m of driving it goes out.

The next things only happen when she is hot, BUT has been left for More than (about) half an hour:

* She struggles to start, just turns over for a while, runs really bad for a few seconds then comes right. This has caused many flat batteries!

* Once she is going, she will randomly cut out, like a sudden jolt, for a split second then carry on fine. This is a very horrible experience.

Some of the things I have done:

* New wheel speed and crank position sensors, new fuel pump, filter, and relay, new (full set) coil packs, iridium spark plugs.

* I have also replaced the manifold seals and the oil separation valve.

I have found water in the car and in the ECU box under the hood, I have dried these out and fixed the leak.

She has only done 108K and I don't want to give up on her, but I'm running out of options.

Have any of you experienced these problems? PLEASE HELP!

[Ahmedsinc 414]

If the DME has gotten wet there's a pretty good chance the root cause of your issues could be in there.

At a guess the traction control light and ABS lights are linked - bad ABS pump?

Running issues could also be faulty MAF sensor and/or cam position sensor/s. Was the crank sensor a new or secondhand item?

I'm no expert - theres plenty more guys around here that know way more than I do - but those would be the first few places I'd be investigating. Hopefully Brent / Grant / Glenn amongst others will chime in

[HELLBM 1552]

Are they diagnosing via The OBD 1 or OBD 2 plug. If both exist in the car i.e under bonnet and in cabin, use the OBD 1 plug to make a connection to the above modules.

[535iase1997 2]

Thanks for the reply,

I was a new OEM crank sensor.

When the lights go out ABS and traction control etc work well. (so I assume the pump is ok).

Only has OBD1. They suggested removing each control module one at a time until I got coms, and I have tried this with no luck so far.

I'm hoping the DME is ok, I've read it takes a lot of work to change them because you need to change the instrument cluster as well.

[BM WORLD 1283]

what year is it ?? , the abs modules all fail on the later ones , I get them repaired all the time ,

if the the ecus have had water near them , they might be toast .

long cranking , some time cam sensor or maf etc .

[535iase1997 2]

A bit of an update on this:

* I found water had been trapped under the passenger seat for months. This caused the following problems (that I know of so far)

- The Yaw sensor for the stability control was under there and was completely shot.

- A lot of earthing terminals are under that seat, including the communication line for the OBD system.

Once I dried out the water, replaced the yaw sensor and repaired the rusty comms terminals, I can now read the entire network of computers!

- This told me that there was a fault with the MAF sensor, I replaced that and now she doesn't randomly cut out!

- It also told me there is an fault with the thermostat, I have ordered a new one, and I am confident this will fix the slow-to-start when hot issue.

It has been a long battle trying to solve all my issues - but thanks to finding that water under the passenger (left front) seat, I am now having some success.

The dealer I purchased the car from knew there was a leak and told me they had a specialist fix it. After calling that specialist, they told me they had never fixed the leak. They went to pick it up, but it didn't start! So the dealer LIED!

Thanks to everyone here that helped, and your suggestions lead to me finding the water.

[Allanw 1071]

The rear door vapour barriers are the most common leak into the cabin, and if under the front seats was wet, and under rear floor carpets will probably be flooded with water too.

[535iase1997 2]

Also I will let you know how the water got in. I will try my best to explain it, as anyone with an E39 may have this issue and not know.

- Just above the ECU (top right of engine bay standing in front of car) is one of the clean air intake boxes for the air con.

- Down the side of it (closest to the side of the car) is a water channel for the water run-off from the front windscreen.

- This channel has a rubber seal to ensure the water from the windscreen runs over the air box and not behind it.

- This seal was missing from my car!

- This is where it gets interesting, the water was running backwards (you know what I mean) and into the metal housing that has the plastic ECU housing inside it.

- It is usually OK for this to happen because the metal housing has drains in it, but in my case they had blocked, due to that seal missing and they were being used every time it rained.

- This metal housing fills with water and the water runs into the ECU box via the positive pressure pump hose hole.

- Once the ECU box fills up, the water then runs down the positive pressure hose, through the fire wall and into the cabin.

- This water flows under the carpet into the foot well. The space between the carpet and the floor in an E39 is quite large and the foam under there holds water very well and it has no way of escaping.

Sorry about the long explanation, but a simple seal can almost write off your car, it also messes with your electrics so bad that you feel like there is no hope.

Please feel free to ask me any questions about this, I am almost an expert.

[535iase1997 2]

I ended up removing all of the seats and carpet (not easy) and letting it all dry for a few weeks. Rear door vapor barriers are perfect.

I also thought it was the sunroof, which was leaking, but I fixed that and water was still getting in.

[Breaker 980]

Bit of a mission, good job on sorting it and the detailed explanation will always help someone else, still gotta love that E39 though right?