ABS light stays on

Post Sun Aug 06, 2006 8:29 pm

Abs light stays on, from moment the ignition is switched on. Checked the relays and they are fine, checked via ones known to work.

What else can it be?

The car has a M50 engine, is it possible to wire in the M50 engine loom in such a way to cause the ABS light to stay on?

Changing over to oil light tomorrow for MOT, but would like to get the abs working correctly, so any help..........please!

Andy

Post Sun Aug 06, 2006 9:06 pm

silly question but is the plug plugged in under the bonnet?

Post Sun Aug 06, 2006 9:15 pm

Love silly questions, here's one of mine...what plug?

The big round plug from the engine is spliced into the e30 loom, there's what I think is the diagnostic plug (got a screw cap? on it) and near the ABS pump is square female 2 pin plug.

Any help?

Andy

Post Sun Aug 06, 2006 9:40 pm

Love silly questions, here's one of mine...what plug?

ill see if i can get you a picture mate tomorrow

Post Mon Aug 07, 2006 12:28 am

Cheers.

Andy

Post Mon Aug 07, 2006 9:32 am

M50 conversion shouldn't cause any ABS problems if wired properly. The red/yellow on pin 20 of the C101 is the ABS feed.
I've only ever come across the ABS light coming on and staying on fault once, and that went away on it's own.
I've read that the problem is supposed to be one of the relays. Two under the ABS cover, and apparently on some cars, one behind the glovebox as well, although I've never found this one either! Don't confuse with the windows/roof relay, or the two dim dip drive light relays.

Post Mon Aug 07, 2006 9:40 am

Yes, did a search and was confident that the relays were faulty.

Checked them with relays known to be good and the light stayed on, had a look for the 3rd relay, but couldn't find it!

Only other thing to mention, when the 6 pin relay is pulled from the ABS pump, the ABS light goes out.

Any suggestions?

Andy

Post Mon Aug 07, 2006 9:56 pm

That suggests that this relay is not energised, as the light can be turned on by the ABS ECU or by this relay.
The relay is controlled by the ABS ECU on pin 27, but what causes it to switch the relay or not, I'm afraid I don't know.

Post Mon Aug 07, 2006 11:16 pm

Sooooo, if I jump the relay with a live feed the light should go out? Or the car'll catch fire

!

And if the light goes out, it's the wiring to the relay from ABS ECU or the ECU itself?

I'll give it a go. Wonder if the problemis caused by the 2 different ECUs not "talking" to each other?

Andy

Post Mon Aug 07, 2006 11:24 pm

ABS only has one ECU (above the glovebox). There's no electronics in the pump/valve unit (behind headlamp).
Relay coil alredy has a live feed. It's the other side of the coil that is earthed by the ECU to operate it.
The light should go out if you earth this (black/white) wire to pin 27, but I don't know what effect this will have on the ECU.