ABS Not Working, No ABS Dash Light On

[DiamondschwarzE30]

I cannot get ABS to work, yet the ABS light on the dash does not come on. I can lock up the brakes and the pump makes no attempt to turn on. The ABS light bulb is not burned out either, it lights up fine with the ignition on/engine off or if I unplug a wheel sensor. Does anyone know what might be causing this? Is there a way to manually activate the pump?

[15Michaeljoseph]

This is pretty weird. Any time I've had an issue with the ABS, the light has come on to let me know. Do you have history on the car, i.e., if the PO was a hack something might be bypassed? There's a relay under the dash that goes bad sometimes, but that should make the light come on. There are also two relays on the ABS unit which I'd also assume would trigger the light. Possibility the pump itself might be no good? I believe there is a way to trigger the ABS, I don't know what it is exactly, but you can likely find it on Google search. Sent from my moto g(6) using Tapatalk

[DiamondschwarzE30]

This is pretty weird. Any time I've had an issue with the ABS, the light has come on to let me know. Do you have history on the car, i.e., if the PO was a hack something might be bypassed? There's a relay under the dash that goes bad sometimes, but that should make the light come on. There are also two relays on the ABS unit which I'd also assume would trigger the light. Possibility the pump itself might be no good? I believe there is a way to trigger the ABS, I don't know what it is exactly, but you can likely find it on Google search. Sent from my moto g(6) using Tapatalk

ABS light was on when I purchased the car. Found out that it was missing switched power from the engine harness relay through the C101 since it is a late model (no relay under dash). Previous owner swapped in a M52 and did not wire the C101 correctly. I hooked that back up and the light turned off. The system gives the illusion that it is working fine, until the brakes lock up. Could it possibly be a seized pump?

[15Michaeljoseph]

ABS light was on when I purchased the car. Found out that it was missing switched power from the engine harness relay through the C101 since it is a late model (no relay under dash). Previous owner swapped in a M52 and did not wire the C101 correctly. I hooked that back up and the light turned off. The system gives the illusion that it is working fine, until the brakes lock up. Could it possibly be a seized pump?

Maybe...? I'm not too knowledgeable on ABS pump anatomy, but if there are moving parts which create those fluid pulses when ABS engages, I'm sure it could possibly be no good. And that might not necessarily be something that would trigger the light because it's the "end result" of the system. Not sure, I hope someone else can lend a hand. Sent from my moto g(6) using Tapatalk

[jgilber0]

I have the same problem with my system and I am getting ready to install a newly rebuilt ABS pump. On my car the ABS light turns on and off as expected but the wheels lock up on hard braking.

Everything I have read suggests that it's the pump. Failures of the control system or sensors will cause the light to come on, but there is no indication when the pump fails. Your pump is likely gummed up with accumulated rust and gelled brake fluid. See this thread for more details:

[DiamondschwarzE30]

I have the same problem with my system and I am getting ready to install a newly rebuilt ABS pump. On my car the ABS light turns on and off as expected but the wheels lock up on hard braking.

Everything I have read suggests that it's the pump. Failures of the control system or sensors will cause the light to come on, but there is no indication when the pump fails. Your pump is likely gummed up with accumulated rust and gelled brake fluid. See this thread for more details:

Thats a very solid point. The more I look into how the ABS pump operates, the more I believe that is the issue too. My brake pedal has been unusually stiff lately and I'm starting to think that a solenoid or check valve somewhere within the ABS pump could be stuck.

[Jordan]

Depending on the year/model and pump PN you have I may have one on hand and ready to ship, if not I can build one to suit and get it out soon. Shoot me a message with a picture of your pump and I'll let you know what the case may be.