ABS fault/light problem

[TriggerFish]

Hi all,

I've got my MOT on Friday, and the ABS is playing up.

I've looked at the Wiki page, but I'm still stumped. The light doesn't work, at all. There's no power coming out of the light connections (checked with multimeter), and the bulb has continuity. I believe the bulb is good - it was working before the respray/strip down.

I've removed the two relays from the ABS pump, and tested them at home with the multimeter and a 12v feed, and they seem to operate fine (I did jump start it, so thought that maybe I'd fried them).

Given that the car's wiring loom will need to be removed after the MOT (to fix another cut corner by the body shop) I've only got the bare essentials plugged in. For the ABS, I've got the ABS ECU, and the earthing point connected, but that's it. Following it's loom back out of the bulkhead, I can't see any other connections that I've missed. It was working fine last June before I took it all apart.

Any ideas gratefully received!

Thanks,
Joe

[TriggerFish]

Cheers for the reply

Sorry, I typed that in a rush at work, so forgot the obvious! It's a 03-1989 325i (Sport, if it matters) with ABS relays on top of the pump, not in the cabin.

And, in living up to your signature, no, I've not yet checked for power to the pump/ECU. I'll give that a go tomorrow, after I've dug out a wiring diagram/ECU pin out. Assuming that there is power, does it point to a dead ECU?

[TriggerFish]

Fantastic, thank you very much. I'm pretty sure mine's the C101 option too - I don't recall seeing anything else heading off the battery terminal.

[TriggerFish]

Power at the C101, no power at pin 10 on the ABS pump. I tried to bridge the pins for the silver relay, but ran out of time.

On the bright side, the ABS light was missed as an MOT failure point, which takes the pressure off so that's something!

I'm look into it again next time I'm at the car.

[Brianmoooore]

Power at the C101, no power at pin 10 on the ABS pump. I tried to bridge the pins for the silver relay, but ran out of time.

Something not right here! No car should have the C101 power source AND the silver protection relay. The former is for the later set up, and the latter is only found in the earlier set up.

[TriggerFish]

OK, I might be getting my relays mixed up then.

On top of the ABS pump, there's two, one black, plastic, standard power switching four pin one, and another, silver, metal six pin one. I assumed this was the power protection relay. The internet states it's a "ABS Pump Timing Relay".



(Like this: http://www.realoem.com/bmw/enUS/showpar ... Id=34_0160)

I take it that the silver thing isn't the cause of my problems, and that the lack of power to pin 10 (for whatever reason), is?

[Brianmoooore]

ABS protection relay, if fitted, should be clipped to the same piece of metal that the glove box catch is bolted to. All ABS pumps have the two relays on top of them.
Power to pin 10 of the ABS pump (red/yellow wire) should be present with the ignition on, and comes from either the protection relay or via the C101, depending on version.
Power should be present on pin 12 of the pump (red wire) at all times, and comes directly from the battery.
Power should also be present all the time on pin 6 of the pump at all times on the later version, and when the ignition is on with the earlier version. If it is not (on the early version) the protection relay has blown.

[TriggerFish]

Brilliant, thanks. No relay on the glove box catch that I can remember.

I guess I've a break in the wire from the C101 to pin 10 then. I'll give that a check once the car is back from the body shop, along with pins 6/12.

Thanks again for the guidance

[TriggerFish]

Right, I've got this fixed, so thought it best to update this.

I went back to basics again, and started checking the bulb with a multimeter. All good.

Then I thought I'd trace the wire to the plug on the ABS ECU, and check continuity. Uh oh. No readings!

So I stripped the loom covering back a bit and noticed that the one green wire (for the light) turns into two for connecting to the ABS ECU. Following it back a bit further, it seems that the green wire goes into a two pin plug, along with a blue wire. Seeing no other plugs in the footwell area, I looked at the accessory socket, and there was a suitably shaped socket, with blue and green wires on the other side. I plugged it in there, and bingo, one working ABS light (and, I hope, system).

Nothing I've seen mentions the ABS having a place on the socket, hence why I never bothered to check.

http://www.e30zone.net/e30zonewiki/inde ... ory_Socket

For reference, it went into ports B & C.

So, TL:DR - it wasn't plugged in.

[Brianmoooore]

Strange that the wiki version of the C302 doesn't mention the ABS plug. I have at least two versions of that diagram in my big "E30 folder", and both of them identify C and G of the C302 as being for ABS.
I'll send Grrr a PM and get it changed.

[TriggerFish]

Strange indeed. It's definately not c and g on mine - it's a connector with two pins, and c and g aren't in adjacent sockets (assuming the pin location doesn't change over the model run).

Unless, of course, the blue wire in the plug was for something else. I've taped the loom back up now, so can't easily check either.

[Brianmoooore]

My C302 diagram of wire colours (taken from an actual E30 in my workshop) shows 'B' as ignition switched live, unfused (plain green), 'C' as D+ from the alternator (plain blue, confirms engine is running), and 'G' (green/red), which is the signal from the brake light switch.