[BLACK E46 SMOKE]

I am having problems with my brakes. At low speeds (1-5mph) when i brake the brake pulsates as if the abs is engaged. Then when i try to pull off it feels as if the brake is engaged and starts to intermittently grab. Once this occurs the DSC, BRAKE, and ABS lights come on and stay on. Once these lights are on i can drive and brake with no problem.

My mechanic thought it was the brake line on the back right tire so i replaced it but this problem still occurs.

Previously i replaced the left front axle and knuckle aka spindle with one from the junkyard. This one came with a sensor so i thought maybe the sensor was the problem so i took out the junkyard sensor and replace it with my previous sensor. The problem still occurs.

I never had this problem until after replacing the left front axle. Anyone know why the problem is?

 

[nk_zhp]

Wheels speed sensor is likely the culprit, but can't be 100% sure. You ABS "thinks" the wheel isn't spinning. This is as I said likely but it's hard to tell for sure.

 

[BLACK E46 SMOKE]

Brakes

Wheels speed sensor is likely the culprit, but can't be 100% sure. You ABS "thinks" the wheel isn't spinning. This is as I said likely but it's hard to tell for sure.

This sounds like it makes sense. My question is if the ABS thinks the wheel is not spinning why would it grab. Isn't the ABS suppose to grab and let go grab and let go to prevent sliding or skidding.

 

[nk_zhp]

I shouldn't have used the word ABS, it could be the ABS DSC, DTC or whatever the marketing team calls the software in the car in this particular moment in time. Bottom line is that since you said the suspension assembly on that wheel was recently touched, chances are, it's either a mechanical issue with the brakes, which based on description doesn't sound like it (it's too "digital" in nature), or some electronic sensor in the area. The Pulse Generator is very likely. It might either be faulty or mis-mounted or badly plugged in.

"Once these lights are on i can drive and brake with no problem." - this statement is a DEAD giveaway that the problem is digital in nature. When the car detects an inconsistent reading from one of its sensors it disables all assist functions. So if the system detected a pulse from 3 wheels but no pulse from one of the wheels it knows something is wrong and it can no longer rely on those inputs to make decisions. The brakes grabbing is likely a DSC response and not ABS, but that's irrelevant.

 

[BLACK E46 SMOKE]

"The brakes grabbing is likely a DSC response and not ABS, but that's irrelevant."

Please explain.

 

[BLACK E46 SMOKE]

"The Pulse Generator is very likely. It might either be faulty or mis-mounted or badly plugged in. '

Where is this? And would this have been touched when changing the axle?

 

[nk_zhp]

The wheel speed sensor or pulse generator using BMW terminology is mounted onto the wheel spindle assembly, where the brake rotor is, but mounted from the back side. The electric wire for this sensor stretched from the wheel spindle assembly to the car's body inside the wheel well resembling the path of the brake lining sensor.

it looks something like this http://media.photobucket.com/image/pulse generator e46/JackChristian/craigslist%20items/IMG_3604.jpg. One side is mounted in the back side of the wheel spindle assembly. So if they removed any front suspension components they likely disconnected the sensor and either forgot to connect it back, or didn't do it correctly. Maybe it got damaged as a result of whatever cause the suspension work but it was not replaced.

Again, this is just some direction to go in, nobody can determine your exact problem via the internet.

 

[BLACK E46 SMOKE]

The suspension work was due to a torn boot. But due to rust the axle was better off being replaced because trying to get it off would have cause a break in it. the new one (used) came with a sensor on it. After this problem started I put the old one back in. Still the problem occurs. Wondering if I damaged the old one when I took it out because it was stuck in the axle. I had to spray it with some loosener the mechanic had and continually turn it back and forth to loosen it.

That pic is EXACTLY what the sensor looks like.

 

[nk_zhp]

So just to be clear, you are saying you had the problem with both the sensor that came on the new (but used) assembly and the one that was on your original/old one?

It is certainly possible that both sensors are damaged in the same way, but likelihood is low. Alternatively the connection itself where this sensor plugs in might be weak, which could explain why both sensors behave the same. The only other possibility is that the teeth inside the spindle assembly themselves have a problem and the sensor is just a victim of misreading the rotation speed of the bearing.

 

[BLACK E46 SMOKE]

I never had a problem with the old sensor until I replaced the axle. If it is the sensor.

 

[Pedi]

Scan the codes or you will be guessing for months.

 

[BLACK E46 SMOKE]

Changed a back left rear tire last night. Before i changed it the DSC, BRAKE and ABS lights were on for a whole week. When i woke up this morning and took off all the lights went off but as soon as i started to brake at the corner the brakes ( ABS) started grabbing again then the lights came back on.

Did the changing of the tire make the lights go out and the sensor react?

2001 BMW 330XI aka Black Beauty