Box above ecu

[Danny-C]

Hi all does anyone know what the box above the ecu does its screwed to the plate that holds the ecu up. thanks .

[BMW_3xx_i]

325e model ?

[Chris-W]

OBC relay box, I'd say.

[Danny-C]

It is a e30 325i 88 model and what does it do im problem solving and wondered what it was thanks

[Chris-W]

Is it black?

[Danny-C]

I think so its only got a few wires bout 5 going in to it. my car has a no spark problem and was changing ecu and noticed it and never seen it, is it for the computer?

[BMW_3xx_i]

can you upload a photo of this box ?

[Danny-C]

not at the mo the car is down mates garage but will try if not sure what it is?

[Chris-W]

Does it look like this?

[BMW_3xx_i]

I've seen this box only in 325e (2,7l 125-h.p.) Motronic 1.0

[Danny-C]

Yes i think it does look like that yes what is it is it for the computer, and it is a 325ise model

[BMW_3xx_i]

it manages an idle control

[Danny-C]

doesnt have anything to do with the spark then have changed most of the other things that do. thanks

[magpie]

excellent read guys,,,,it's not that then [no spark] crank sensor?

[Danny-C]

Na done crank sensor, pulse sensor, ecu, dizz, rotor, coil, leads, plugs, earths, u name the norm ive tried it.

[magpie]

not good m8 did the bits you change come off a running car????

[Speedtouch]

Just a thought, does your car have an OBC, because it has a CODE function (immobiliser) that can be used to cut the ignition - if it's playing up, it could be causing your problem.

I'd also suggest ensuring that the ECU is getting a firm +12V feed from the ignition switch - if the switch is worn out, it could be causing an intermittent supply.

[Danny-C]

That sounds good how do i test the ecu is getting a good 12v cause it is a intermittent fault somethimes it works and somethimes nothing.
Yes it does have the OBC but never seen the code bit come up how could i resolve that can i just change the OBC ecu box that manages it.
Magpie all parts are off a working car and have also had it plugged into the bmw fault finder still nothing.
Thanks guys

[Brianmoooore]

Connect a piece of wire between the + terminal on the coil and the phantom battery + terminal on the bulkhead (without disconnecting anything), and see if the car will start.
Box is part of the OBC and nothing to do with idle control.

[Danny-C]

Hi Brianmoooore i tried that wire between coil and + battery and it did seem to make a difference what is the next step in sorting that out

[Speedtouch]

The +12V is supplied to pins 18 and 37 of the 55-pin Motronic connector according to this diagram http://www.autolib.diakom.ru/CAR/BMW/19 ... /fig02.pdf

You could unplug the ECU and test for a reliable +12V feed to these pins using a multimeter or test lamp. Don't forget, although pin 18 is permanent +12V, pin 37 is ignition switched, so will only activate when your ignition key is turned to the appropriate position(s).

[Brianmoooore]

Hi Brianmoooore i tried that wire between coil and + battery and it did seem to make a difference what is the next step in sorting that out

What do you mean by "it made a difference"?
Did it start or not?

[Danny-C]

Yes it did start but it has been starting again now but runninng rough but was a lot better when the 12v coil was connected to the main 12v+

[Brianmoooore]

The next time it won't start, connect up the battery to coil lead again and see if it starts.
For intermittent and poor running, the DME (white) relay is suspect.

[Danny-C]

I can turn the car over and it doesnt start or if it does it cuts out then whilst turning put a live to the coil and it will fire straight away. will check dme now

[Danny-C]

Tried changing the relay doesnt make a difference so just to reiterate turning car over nothing happens keep turning and put a 12+ to the coil and she starts up straight away different relay didnt work.

[Brianmoooore]

If connecting the battery+ to coil + wire makes a difference, then remove the panel above the glovebox and find a two pin connector hanging from the loom above with two green wires going to it (one to each pin). Disconnect the plug that goes into it, and search around the loom nearby for an identical plug doing nothing.
This plug will have a loop of green wire connected to it and just be tied up to the loom. Pull it free and push it into the socket, so connecting the two green wires from the loom together.
If the spare plug isn't there, use the one that's already plugged into it, and short the wires together.

[Danny-C]

ok will check that now what is that doing/ connected to.

[Danny-C]

your a legend i think that has done it it seems to be better now. The test will be when i go back to it and see if it will start again, Will let you know how i get on many thanks again dan.

[h2700]

[quote="Speedtouch"]Just a thought, does your car have an OBC, because it has a CODE function (immobiliser) that can be used to cut the ignition - if it's playing up, it could be causing your problem.

do u know anything more about this ? i have a similar problem and i believe this is my problem lol

[Danny-C]

I dont know if this is the problem. what are your symptoms. But if it is the same i think ive fixed mine. with that wire trick that Brianmoooore said about but not sure excatly what that does.

[h2700]

just done the same thing to mine and sorted it think the obc unit has packed in

[Danny-C]

what was your car doing

[h2700]

just put a 2.7in . tryed to start it and it would turn over but there was no power at the coil so there was no spark so it wouldnt start ,

checked the ecu and found there was no ignition live onto to the ecu (pin27) followed that back and found that the was power on one side of that white plug and no power on the other side , followed that plug back to the relay box for the obc , im guessing the obc code function has either enabeled or that because the cars been sat in bits for quiet a while its reset itself or sumit ?

mines running ok i think now not tested it as im waiting for a chip from ant, as the one i had originally from ebay was a fake i think

[Danny-C]

nice on mine been giving me trouble for 2 months now been getting worse hopefull now sorted