ABS light on

[Ceeker]

So I took out my cluster because when I got the car someone else was messing around behind it. I plugged what wasn't plugged in and got an ABS light after reinstalling it. nothing out of the ordinary but wondered if this is could be the ABS relay?

Is the ABS relay silver with 4 prongs?

any help would be appreciated. thx

Update: replaced all 3 relays: two on the pump and one under dash.
Replaced the control unit
Replaced the faulty right abs sensor. we did a resistance reading with a tester.
ran car to test voltage from alternator. idle test read: 13.6 volts.

the light remains on...URGH!!!!!!

[Semblance]

My ABS relay is silver, mounted behind the knee bolster under the steering wheel. I believe ive seen that replacement relays can be black plastic though. Search, lots of info on DIY incl pics. You have to open the silver case to see if the little wire fuse is blown. I did the soldered-in fuse holder being too cheap to buy a new relay, worked great for me. The relay is irritating to pull out but otherwise an easy fix.

[Ceeker]

My ABS relay is silver, mounted behind the knee bolster under the steering wheel. I believe ive seen that replacement relays can be black plastic though. Search, lots of info on DIY incl pics. You have to open the silver case to see if the little wire fuse is blown. I did the soldered-in fuse holder being too cheap to buy a new relay, worked great for me. The relay is irritating to pull out but otherwise an easy fix.

Hey, thanks for your input; I did locate and remove the silver relay. Apparently this is a common problem with these from what I've been told. I have a spare which I will just replace to check and test first. seems like an easy enough fix and why give bmw more money as they take enough as it is..LOL

[willworkfore30s]

Just an FYI. I had an ABS light in my 318is (doesn't have the silver relay). I pulled the bulb and just decided not to worry about fixing it. Then when I was doing suspension work I realized my ABS wheel speed sensor on the drivers side was broken. So if the relay doesn't fix your problem, you could give those a look.

[Ceeker]

Just an FYI. I had an ABS light in my 318is (doesn't have the silver relay). I pulled the bulb and just decided not to worry about fixing it. Then when I was doing suspension work I realized my ABS wheel speed sensor on the drivers side was broken. So if the relay doesn't fix your problem, you could give those a look.

Well, I replaced the relay and out of curiosity I opened both just to see and the original one was fried. I installed the 2nd one and I still have the light on so this tells me it must be the abs sensor. I got a few spares of those as well and since I am replacing the rack I might as well change the sensor while in there.

thanks for input.

[Ceeker]

Just an FYI. I had an ABS light in my 318is (doesn't have the silver relay). I pulled the bulb and just decided not to worry about fixing it. Then when I was doing suspension work I realized my ABS wheel speed sensor on the drivers side was broken. So if the relay doesn't fix your problem, you could give those a look.

well, I changed the front abs pulse sensor and I still have the light on. BUT! I did notice the left front caliper is not letting up. unless the caliper is causing this I can only draw one last conclusion and that it's the control unit causing the problem?

[nrubenstein]

There are four ABS sensors. To test them, start by unplugging three. Drive the car. If the ABS light comes on, then that sensor is probably working. Repeat until you have a sensor that doesn't cause the ABS light to come on.

[Ceeker]

ok will do...thank you.

[nrubenstein]

ok will do...thank you.

Note that if the ABS light is on before you move, then you probably have another issue (although it is possible for a really fucked sensor to do that).

[Ceeker]

ok I checked all the sensors and the right front was bad; used a multimeter to check. replaced it and still I have a light. Drove it for a long time and turned the car on and off to see if it would cycle off. No dice. So I'm guessing it could be the control unit or the pump itself?

[Ceeker]

update: changed the relay, changed the control unit, changed the right front ABS sensor as it was faulty. Disconnected the battery thinking maybe it would reset the system. Upon starting the car, the abs light still remains on. I also changed the two relays that sit on top of the abs pump.

anything else I can do?

[FLG]

Did you use a new relay?

Sent from my Galaxy Nexus using Tapatalk 2

[Ceeker]

Did you use a new relay?

Sent from my Galaxy Nexus using Tapatalk 2

the relay I used is used but good working relay. I opened it and checked the fusible link.

[jlevie]

Troubleshooting the ABS system isn't very difficult. It is a standalone system
that only gets input data from the brake light switch, wheel sensors, and
system power. The parts of the system are the ABS module located next to the
steering column, the ABS relay mounted above the ABS module, the ABS unit in
the left front of the engine bay, and a speed sensor at each wheel.

If the ABS light comes on with ignition, but doesn't go out when the engine
starts, a wiring problem, bad module, or bad ABS relay are the likely
candidates. A failed or weak alternator will also cause this because the
system voltage won't rise enough. There is a fusible link inside the ABS relay
that can be blown. The relay can be repaired, or better yet, replaced.

If the ABS light comes on when you turn on the ignition, goes out when the
engine starts, and then comes back on before the car is moving the cause could
be a bad module, a bad ABS unit, or a wiring fault.

If the light goes out after engine start and only comes on when the car is
moving, there's a problem with one (or more) of the sensors. The simple test
to find out which sensor(s) is the cause is to disconnect all but one of the
sensors and drive the car. If the light comes on, that sensor is sending a
speed signal to the ABS and is good. Repeat with each other sensor to find the
one(s) that don't cause the light to come on. Since the ABS module has no
speed input besides the wheel sensors, if only a bad sensor is connected the
module can't tell the car is moving and thus doesn't fault on missing speed
signals from the other wheels. Once a bad speed sensor is found, if a new
sensor still doesn't work, there could be a wiring fault in that circuit or a
bad input channel in the ABS unit.

[Ceeker]

well, we by passed the control unit to a good power source and the abs light went out.
This leads me to believe one of two things. a) a break in the wiring harness somewhere or b) possible faulty 2nd relay installed. I am going to see if power is going to and from the relay.

Problem solved: right front ABS sensor was faulty but also the thin wire was broken in the relay. To determine this I tested the power coming from and going to the relay. I only received power in. There are 3 power sources and 2 grounds from the relay. the red/yellow is the power source which sends the signal to the dash for the light to go out and to the control module.

After removing and soldering the relay - reinstalled it - tested with the multimeter with ignition on the red/yellow lead had power coming out. after plugging the control unit back in the light went out.

appreciate everyone's help!!