Problem with Pad Wear Sensors

I've had my Brembo GT's on for 1.5 years now.. The OEM pad wear sensors are tied off on the strut because the Brembo pads don't support them..

Everything had been fine until a couple of weeks ago.. i-drive warning light came on that my pads were low and I needed to go in for service.. HA!

The wheels came off and the sensors still looked fine zip tied to the strut.. just to be safe, I bought a new set anyways (2 in front) and put them in...zip tied to strut again.. I also did the procedure to reset the service lights.. with the odometer and BC button..

I thought things were cool again but after a few miles it comes back on again!?! ... with the new sensors this time.. What could be wrong? Do I have a faulty sensor box? Anyone experience this with their aftermarket brakes? Am I missing something?

--mike

I just wanted to add that the sensors are plugged into the little black box.. just not attached to the pads

leemik wrote

I just wanted to add that the sensors are plugged into the little black box.. just not attached to the pads

The chassis computer estimates pad wear from the amount of driving and stopping you do. The sensors only confirm what the computer figures out on its own.

I have a BBK with the sensors tied back like yours. One track day can drop my "miles to go" on the CBS by two or three thousand miles. I drop by the dealer to have my warning light reset after every track season.

You didn't need to replace the sensors - they were fine.

Interesting... I can reset all service mileage myself via "secret" service menu.. Odometer + BC stalk button(including the pad wear warning mileage).. but you also actually have to have it plugged into another computer too?!?

thanks for the tip I'll stop by BMW in morning..

JAJ wrote

The chassis computer estimates pad wear from the amount of driving and stopping you do. The sensors only confirm what the computer figures out on its own.

I have a BBK with the sensors tied back like yours. One track day can drop my "miles to go" on the CBS by two or three thousand miles. I drop by the dealer to have my warning light reset after every track season.

You didn't need to replace the sensors - they were fine.

leemik wrote

Interesting... I can reset all service mileage myself via "secret" service menu.. Odometer + BC stalk button(including the pad wear warning mileage).. but you also actually have to have it plugged into another computer too?!?

thanks for the tip I'll stop by BMW in morning..

I'm not sure what's required - all I know is that the dealer techs just set the "mileage to go" on the brakes back up to 10K or so, and its all fine for another year. I have them do it at the annual oil change service.

I'm having the same issue with my Stop Tech brakes. I have the BT tool, maybe that will clear it?

If you've reset the maintenance interval properly, check to see if your sensors are connected correctly. There could be a problem with the wiring.

JAJ wrote

I'm not sure what's required - all I know is that the dealer techs just set the "mileage to go" on the brakes back up to 10K or so, and its all fine for another year. I have them do it at the annual oil change service.

OK I bet all they are doing is the "odometer-BC stalk" procedure that I'm doing.. you can access all of the "mileage to go" items there and reset it yourself..

Now I'm wondering if there is possibly something wrong with the sender box.. i mean the wires are so simple to plug in even a caveman could do it and the original wires were never unplugged from the box side but they tripped..

the only other thing that makes sense to me is if there truly is another reset needed for the computer with a BT tool only... makes no sense that there would be two such checks however.. talk about over engineered.. I hate computerized cars, so difficult to do anything to them these days..

--mike

I've reset my brake fluid interval using the odometer-BC stalk, and it worked fine. So I don't think you need a BT tool to reset...

This is just an update to the problem.. I've been dealing with it for the last 2+ months now

The "brake" light will not go off no matter what I do..and now the rear sensor is tripped too.. I brought it to the dealer to see if maybe they have to hook it up to a special tool to reset.. They tried but could not shut off the light.. They even plugged in 4 new sensors to rule out the possibility my "new" sensors are bad.. but they still could not shut of this light.. they said they ran some diagnostics and said everything was working properly except the system was stuck in a closed loop and would not come out of it.. They flushed and rebleed the brakes also (covered under scheduled maint) and light still illuminated =(

They said there's nothing else they can really do. There is a software update /recall for my car coming up.. so we are holding out a small ray of hope it's some sort of software glitch or bug that can be resolved by this.

--mike

leemik:

Sorry to hear you are having trouble with this. It does seem odd, based on what you have described.

FWIW, back in May of 2008, I was the first in NA to install the Brembo 380mm kit and I have not had any such issues since. I think this problem is an anomoly.

Have you tried re-installing the OEM system to see if it persists? If it does, I would leave the system on and take it in to a different dealer to be repaired. I'm not sure that I could accept the previous "...There's nothing else we can do..." statement from the other SA. I also doubt the upcoming software update they mentioned will affect this.

Good luck with this and please keep us posted.

It's probably a long shot, but I remember messing with iDrive ('08 here) and found that I could change one interval without the BC and dash buttons, but don't remember which. Go to the service menu and try to change it. As far as I know, the service light is only triggered by the (tripped) sensors, but could be wrong. If that doesn't work, it has to be one of the modules, but it's incredible to hear from a freaking dealer they can't fix it . That kind of moronic 'diagnostics' is what scares me the most about keeping my car after warranty. It's not only how expenisve some of the failures can be, but imagine having to pay for hours of troubleshooting time on top of everything else?

I also reset the brake fluid service, even though I did it early (it was postponed for 2 years after I did it, which was nice). Also changed the inspection date to 4 years away, or something like that, so it doesn't bug me for a while .

elp_jc wrote

It's probably a long shot, but I remember messing with iDrive ('08 here) and found that I could change one interval without the BC and dash buttons, but don't remember which. Go to the service menu and try to change it. As far as I know, the service light is only triggered by the (tripped) sensors, but could be wrong. If that doesn't work, it has to be one of the modules, but it's incredible to hear from a freaking dealer they can't fix it . That kind of moronic 'diagnostics' is what scares me the most about keeping my car after warranty. It's not only how expenisve some of the failures can be, but imagine having to pay for hours of troubleshooting time on top of everything else?

I also reset the brake fluid service, even though I did it early (it was postponed for 2 years after I did it, which was nice). Also changed the inspection date to 4 years away, or something like that, so it doesn't bug me for a while .

when you reset your service light for the brakes, do you need a scan tool to do this or can you just do it through the BC stalk? what is this "secret" menu that everyone is talking about ??

sorry but i am quite ignorant on this issue but i have a bbk on order and would like to know how to reset the mileage on the brake maintenance when i need to do so.

leemik wrote

OK I bet all they are doing is the "odometer-BC stalk" procedure that I'm doing.. you can access all of the "mileage to go" items there and reset it yourself..

Now I'm wondering if there is possibly something wrong with the sender box.. i mean the wires are so simple to plug in even a caveman could do it and the original wires were never unplugged from the box side but they tripped..

the only other thing that makes sense to me is if there truly is another reset needed for the computer with a BT tool only... makes no sense that there would be two such checks however.. talk about over engineered.. I hate computerized cars, so difficult to do anything to them these days..

--mike

i completely agree. i hate how there's a computer monitoring everything. people should learn how to check how much brake pad life they have in their cars by themselves.

Here's some instructions. BMW recommends resetting using diagnosis system, but it is not required.

Resetting the service items

Observe the following process for resetting:

Switch on the ignition (terminal 15)

Press the trip odometer for approximately 10 seconds until the first CBS item appears.
(The next item is reached by briefly pressing the button again)

If the value is to be reset, press the button again for approximately 3 seconds until ”Reset?” appears.

Reset is confirmed by pressing the button again for 3 seconds.

Note:

The reset process is cancelled by waiting for too long or by replacing the terminals.

CBS items are arranged chronologically. The most critical item is displayed first.

Every reset causes the service counter of the respective item to be increased by one. The service counters are used in the item-specific SAM to monitor additional work.

Important:

It is only possible to carry out a reset in the vehicle if the service life of the item is below 80%; if however it is necessary to carry out a reset, this must be done in the diagnosis system (see ”CBS reset with the diagnosis system”). The reset lock is displayed in the menu with the text ”O.K.”.

The values should only ever be reset after the service measure has been carried out.

Every time CBS items are reset, it must be ensured that the on-board date is set correctly. The on-board date is the reference for defining the target date for the time-dependent CBS items.

If the on-board date needs to be corrected, the service order must be checked again.

It is only possible to reset the front and rear brake pad displays if the brake pad sensor is working.

Correction of the legally stipulated (§) values is carried out in the Control Display.

^^ that sounds very similar to the "BC-stalk" procedure

when i access my brake service light in BC stalk the service mileage interval says " " for both the front and rear warning.. and hitting reset does nothing, the brake light is still illuminated. Not sure if it's supposed to be like this as everything seems to have a mileage attached to it in that display.

The brakes were installed for over a year without incident when this suddenly happened.. I can say one thing, it started about 2 weeks after a new software revision was put into the car (I have the dct and complained about slow 2nd gear shifts)... coincidence? dunno.. that's why the dealer is holding out hope that a newer revision possibly fixes this.

One thing that happened after getting this revision is the iDrive cuts out on me intermittantly as well.. the system glitches like "the matrix" and then just shuts off totally.. it won't go back on sometimes until the next day. It's happened to me about once a month.. of course dealer can't replicate

HATE these computerized cars.. In the end humans are still much smarter.

This is interesting and a bit disturbing as I've got an APracing BBK in the mail. Although the dealership did everything they could to reset it, including connecting new wires to the brake wear sensors. I wonder if connecting new OEM pads to the wire sensor clips while stationary would resert it? Is there a ground or "closed loop" that the signal from the wires has to have in order to not trip the light? or is it the other way around, where once they make contact as if warn down, then the system is closed and causes the light to trigger? I've not seen first hand how the brake sensor is built, but will I guess when I remove them soon.

Hmmm perhaps MOD is not so ... ?good

BimmerRob08 wrote

This is interesting and a bit disturbing as I've got an APracing BBK in the mail. Although the dealership did everything they could to reset it, including connecting new wires to the brake wear sensors. I wonder if connecting new OEM pads to the wire sensor clips while stationary would resert it? Is there a ground or "closed loop" that the signal from the wires has to have in order to not trip the light? or is it the other way around, where once they make contact as if warn down, then the system is closed and causes the light to trigger? I've not seen first hand how the brake sensor is built, but will I guess when I remove them soon.

From what I gather.. the system is a open circuit.. until the pad wears down enough where the two ends on the sensor comes in contact with the rotor or what ever metal it comes in contact with and completes the circuit tripping the warning light.

It sounds like I'm the only person with a BBK that is unable to shut this light off?? WSTO did tell me that Brembo is rumored to have a pad coming out soon that supports the OEM sensor so we don't have to tie it off to the strut anymore...it was just wierd that it worked fine for so long then. suddenly i can't shut it off no matter what i do.. and the only real difeence was the a BMW software update

leemik wrote

From what I gather.. the system is a open circuit.. until the pad wears down enough where the two ends on the sensor comes in contact with the rotor or what ever metal it comes in contact with and completes the circuit tripping the warning light.

It sounds like I'm the only person with a BBK that is unable to shut this light off?? WSTO did tell me that Brembo is rumored to have a pad coming out soon that supports the OEM sensor so we don't have to tie it off to the strut anymore...it was just wierd that it worked fine for so long then. suddenly i can't shut it off no matter what i do.. and the only real difeence was the a BMW software update

I could be wrong -- I always understood that the system was a closed circuit. When the sensor comes into contact with the rotor, it wears through the wire and interrupts the circuit, thereby triggering the warning. I would think this would be much more reliable that an open circuit system as continuity through the rotor could be intermittant.

Does anybody know for sure?

Well I'm not an electrision but an ex-jet engine tech that had to work and trouble shoot some electronics to a degree. Unless I've learned the opposite all these years, a system like this is considered a "closed" loop. Because once the two contacts make contact, it closes the loop and triggers a fault or caution light. That's how I understand it.

But regardless, I hope the OP can get to the bottom of this issue. I really doubt re-installing the OEM brakes would make a difference. That's why I mentioned maybe put the car on jacks, remove the wheel(s), reconnect the OEM pads to the sensors that way it'll fool the system to think it's got OEM pads on. I've not seen the construction first hand either than photo's but It don't look like any part of the sensor touches any part of the caliper or disc. Either wise it would ground out and might not operate correctly.

Thinking of that, maybe he should try to ground out the sensors and see if that does the trick. It's process of elimination. Might work:confused2

leemik wrote

They even plugged in 4 new sensors to rule out the possibility my "new" sensors are bad

You have 4 sensors? I only have 3. Two up front and one on the passenger rear.

FWIW, when I change my pads for taking the car to the track I have an extra set of sensor "capsules" with the actual sensor & line snipped off that get plugged in. It keeps the warning lights from coming on. Don't know if that helps determine open or closed system..?