ABS Schematic

[wodcutr]

My ABS light will not go out in my sons 89 325i build date 7/88. I have verified the relay is functioning as it has one permanent red hot with key off and with key on the other side of the relay gets hot (2 red/yellow) along with the green center wire that goes to the dash.

My Bentley manual does not have a wiring schematic for the abs and I am trying to find where the two red/yellow wires go to after the relay. I am suspecting there is a short in one of them. I have 3 abs computers and none of them do anything different when installed, so I suspect that the wire going to the computer is bogus but I do not know what pin to check on the connector to see if I am right.

If anyone has a pinout for the abs could you please forward it to me. Thanks in advance!

[TobyB]

http://www.wedophones.com/BMWManualsLead.htm

t

[BMWManiac]

If the relay above the computer is fine, then it is either the relays on the ABS pump itself, or the controller itself

[wodcutr]

Thank you for the abs schematic Toby. I was able to verify that I am indeed getting power through the relay into the computer on pin 1 and to the pump on pin 10 with ignition on so I am really stumped now!

I have swapped in three different computers and the light won't turn off. Also tried three different pairs of relays on the pump itself and still no worky. I even tried installing another pump without attaching the brake lines to it, but had all electrical connected and started the car and still the light stays on.

I can't figure out what the problem is. What turns the light on with ignition on and turns it off after starting? I am assuming the computer has some checks in it to verify the system is working and then turns the light off. What pins should I check to see if the computer is getting the correct inputs or not?

[jeffnhiscars]

I'd have to brush up on my ABS101 but I believe that a faulty ABS wheel sensor will cause the light to stay on and that it should turn off when you hit 6mph. There's a test method that jlevie posted (of course who else) that I think has you disconnecting one at a time, running up to 6mph and seeing if the light goes out....or something like that.

[wodcutr]

That's for finding a bad sensor that sets the light off once moving. You unplug all sensors but one and drive, repeated until the light does not come on. That would be the bad sensor. If you start the car with all the sensors unplugged the abs system will think all is functioning properly even if you drive the car, as it won't know you are moving. I have tried unplugging all sensors before starting the car and still the light stays on.