ABS Relay Wiring

[603Racing]

My ABS relay light came on a while back. I picked up a new relay and finally got around to replacing it yesterday. My problem... i can't find the damn relay to replace it. I have the lower bolster removed. I also took out the ABS controller, pulled wiring out of the way, removed the lower cover of the steering column... nothing. I even started looking behind the climate controls, above/behind the glove box, and in the engine bay.

I know my ABS worked before as I was testing it out on a rainy day this past spring.

The only thing I found was a bundle of five wires that were cut and taped. Can someone tell me what the color the wires are that go to the ABS relay? I'm not sure how my ABS worked without the relay, maybe it's hard wired (bypassed relay)... if it would even work that way.

[nrubenstein]

Many '89s (probably from 1/89, but the cutoff date is uncertain) and all airbag cars do not have a relay. There is a fusible link in the ABS brain. If the brain has a red label, you can easily tell that the car is airbag style (as my 2/89 car is).

[jlevie]

The relay should be just above the ABS module

[603Racing]

My car is a '90 and I do have a red label on my ABS module.

Jlevie, I did have the module pulled out of the car and there was no relay on it as I had expected there to be. If Nrubenstein is correct then that makes sense.

I did not know that late e30's had no relay for ABS.

[nrubenstein]

My car is a '90 and I do have a red label on my ABS module.

Jlevie, I did have the module pulled out of the car and there was no relay on it as I had expected there to be. If Nrubenstein is correct then that makes sense.

I did not know that late e30's had no relay for ABS.

The first thing to do is open up the brain and make sure the fusible link is intact. After that, ohm out the sensors. The ABS light comes on for ANY system malfunction, so the most likely issue is that you've got a bad sensor.

[603Racing]

My guess is the link, under the assumption that it's as sensitive as the relays are. The ABS light came on after a motor swap. I'll start with the link and go on from there. Thanks.

[nrubenstein]

My guess is the link, under the assumption that it's as sensitive as the relays are. The ABS light came on after a motor swap. I'll start with the link and go on from there. Thanks.

Wait, stop. What was the motor swap?

The late model ABS unit gets its power through the engine harness. The real issue is likely that you have not powered the ABS system at all.

Edit: As I recall, C101 pin 20 needs SWITCHED 12v power. You should confirm the pin, because throwing unfused power down the wrong pin would suck ass. In an E36 S50 harness, switched 12V is available from the red/white wire splice junctions.

[603Racing]

I swapped in a m20 from an '89 that has a black label ABS. Let me go check to see which harness I ended up using... it's been a few months and can't recall off the top of my head. I should be able to find out shortly.

[603Racing]

I used the '90 harness. The '89 (parts car) has a black label ABS module. I'd rather check for power first before I pull the module apart. Which pin on the module connector is the switched 12v power?

[nrubenstein]

Download the ETM from wedophones.com or various other places and take a look through.

[603Racing]

I will take a look, thanks.

On a side note... I've seen your signature pic dozens of times and just noticed the yellow flag which then made me notice the hood of your car. Very nice.

[nrubenstein]

I will take a look, thanks.

On a side note... I've seen your signature pic dozens of times and just noticed the yellow flag which then made me notice the hood of your car. Very nice.

Yeah, that was my entry into the hood pin club. Here's the video: http://www.youtube.com/watch?v=cNYFTkqgfRQ

Oops pretty much sums it up. :)

[603Racing]

Back on this topic. I swapped the module with another and the light is still on. After rethinking my steps, I'm pretty sure I did use the '89 harness after all. That would make it the only thing that is different after the swap. And from my last few years of racing, I've learned that the most recent change is likely the cause of the new issue that has just occured.

I did take apart the ABS module and did not see any visible signs of failure. I will check for power.