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      12-02-2011, 11:50 PM   #1
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Brake pad sensor Question

Yes I searched, and only found one thread that addressed this. Am I understanding this correctly, someone please...


I have about 50% pad life right now F&R. I just bought some Akebono Euro pads for the F&R. Do I need to buy new sensors? Or can I reuse them? I'm still not 100% sure if the new sensors start wearing during the pad life, or if the sensor "self destructs" to ignite the pad service light. I'm looking for a in depth description of how the sensors work.

Edit: After searching around on the net, looks like if the brake pad light never went off, the sensor is still good. The computer is computing it's predictions based on input from your driving and estimates it pretty much and then once the little sensor rubs off on the rotor, light comes on, you just bought a sensor. So I'm betting I can re-use my sensors and reset the brake pad service in the dash for each the F & R. So it's very similar to a GM oil light, minus the sensor that burns out on contact.
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Last edited by fl335i; 12-03-2011 at 12:03 AM.
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      12-03-2011, 12:50 AM   #2
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Change your pads over 50% and your sensors will never touch the rotors

If you do not change your sensor cable please do not reset your CBS - your brake warning and SES will light up like a Christmas tree.

Last edited by Glim; 12-03-2011 at 02:42 AM.
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      12-03-2011, 08:38 AM   #3
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^^^ WHY? HOW? I don't follow that. Isn't it the same thing as resetting your oil meter half way?
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      12-03-2011, 09:07 AM   #4
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So what you're trying to say is if you don't trip the brake sensor, you can reuse it?
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      12-03-2011, 01:13 PM   #5
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So what you're trying to say is if you don't trip the brake sensor, you can reuse it?
Correct, the sensor does not touch the rotor until 50% pad life. The CBS system will not increase pad life but it will not decrease until the sensor starts to wear.

If you reset the brake CBS without changing the sensor you will get a "car on a lift" warning and a "brakes at ---- km/mi" when you start the car.
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      12-03-2011, 02:17 PM   #6
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huh. So I probly need to look and see if my sensors are worn or not.
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      12-03-2011, 02:29 PM   #7
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So you need to understand how the brake pad monitor system works. It is dual stage, which means the pad wear sensor has two wires in it to break at different times. The first wire is in front of the second wire (as they are facing the pad). When the first wire breaks after contacting the brake rotor the computer senses the change in resistance of the circuit. The computer loggs this event and uses the mileage recorded along with other variables to estimate when the pads will need replacement. This information is then displayed on the CBS notification. Once the second wire is broken after contact with the rotor, the dash light for pad replacement comes on and stays on. If you replace the sensor with a new sensor before the second wire is broken in the old sensor, you can screw up the CBS computer's expected second wire breakage event. My advice is to use the old sensor until it breaks the second wire (in dicating the new pads you've just put in are worn out). Or you could by a new sensor and shave it down until the 1st wire is broken, that my trick the computer into thinking the sensor has not been replaced.

Last edited by ENINTY; 12-04-2011 at 07:14 AM.
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      12-26-2011, 09:31 PM   #8
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I made the mistake of resetting the the brake mileage when I changed my rear brakes and sensor. I ended up getting the "car on lift", brake warning light and "----" miles indicated for next brake change After reading the different threads and Bentley manual stuff on this I finally found a way to fix this.

The system looks for two "untriggered" sensors when you reset the brake service mileage. If it sees even the preliminary trigger on any of the sensors it will give you this error. The preliminary trigger as stated above does not mean that there is no brake pad left. In my case the front pads had at least a little under 50% life left in them and therefore I did not replace them or the sensor. So this is what I did to fix it.

I took the old sensor I just removed from the rear and cut of the sensor portion. I then stripped the two wires back and twisted them together which creates a short and mimicks the reading a new sensor gives. Unplug the partially used sensor at the socket connection on the car (not the brake) and plug in the shorted old sensor. Do the brake reset procedure and you will get the appropriate mileage restored. Go back and remove the shorted sensor and plug back in the partially used sensor. At this point everything should be back to normal with the new sensor showing 90,000 miles and the partially used sensor showing whatever miles that were there before you created the error.

Hopefully this helps you. I think you should be able to use this procedure to reset the front or rear sensor one at a time without having to replace both sensors.
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      12-27-2011, 08:51 AM   #9
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Quote:
Originally Posted by 3Coupe4Me View Post
I made the mistake of resetting the the brake mileage when I changed my rear brakes and sensor. I ended up getting the "car on lift", brake warning light and "----" miles indicated for next brake change After reading the different threads and Bentley manual stuff on this I finally found a way to fix this.

The system looks for two "untriggered" sensors when you reset the brake service mileage. If it sees even the preliminary trigger on any of the sensors it will give you this error. The preliminary trigger as stated above does not mean that there is no brake pad left. In my case the front pads had at least a little under 50% life left in them and therefore I did not replace them or the sensor. So this is what I did to fix it.

I took the old sensor I just removed from the rear and cut of the sensor portion. I then stripped the two wires back and twisted them together which creates a short and mimicks the reading a new sensor gives. Unplug the partially used sensor at the socket connection on the car (not the brake) and plug in the shorted old sensor. Do the brake reset procedure and you will get the appropriate mileage restored. Go back and remove the shorted sensor and plug back in the partially used sensor. At this point everything should be back to normal with the new sensor showing 90,000 miles and the partially used sensor showing whatever miles that were there before you created the error.

Hopefully this helps you. I think you should be able to use this procedure to reset the front or rear sensor one at a time without having to replace both sensors.
Just so I understand this: If I didn't mind pissing away $$$ and went ahead and replaced both sensors anyway, this wouldn't be an issue, right?
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      12-27-2011, 09:52 AM   #10
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Quote:
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Just so I understand this: If I didn't mind pissing away $$$ and went ahead and replaced both sensors anyway, this wouldn't be an issue, right?
Correct. If you went ahead and replaced both sensors then all this is mute. In my case I did not know this and only ordered the rear brakes and sensor because that's what was needed at the time.
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      12-27-2011, 10:17 AM   #11
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Correct. If you went ahead and replaced both sensors then all this is mute. In my case I did not know this and only ordered the rear brakes and sensor because that's what was needed at the time.
Gotcha... thanks!
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      01-30-2012, 04:57 AM   #12
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Quote:
Originally Posted by 3Coupe4Me View Post
I made the mistake of resetting the the brake mileage when I changed my rear brakes and sensor. I ended up getting the "car on lift", brake warning light and "----" miles indicated for next brake change After reading the different threads and Bentley manual stuff on this I finally found a way to fix this.

The system looks for two "untriggered" sensors when you reset the brake service mileage. If it sees even the preliminary trigger on any of the sensors it will give you this error. The preliminary trigger as stated above does not mean that there is no brake pad left. In my case the front pads had at least a little under 50% life left in them and therefore I did not replace them or the sensor. So this is what I did to fix it.

I took the old sensor I just removed from the rear and cut of the sensor portion. I then stripped the two wires back and twisted them together which creates a short and mimicks the reading a new sensor gives. Unplug the partially used sensor at the socket connection on the car (not the brake) and plug in the shorted old sensor. Do the brake reset procedure and you will get the appropriate mileage restored. Go back and remove the shorted sensor and plug back in the partially used sensor. At this point everything should be back to normal with the new sensor showing 90,000 miles and the partially used sensor showing whatever miles that were there before you created the error.

Hopefully this helps you. I think you should be able to use this procedure to reset the front or rear sensor one at a time without having to replace both sensors.
Please help me. I recently replaced the front brake pads because they were worn, but noticed that the sensor was still untriggered. I did not buy a new sensor, but I did not want to reuse the old one either, so I wrapped the sensor portion with electric tape and zip-tied it somewhere inside the wheel well without inserting it back into the brake caliper.

I put the wheels back on, and went ahead to reset the CBS. DING! The SES and brake lights are on. What have I done wrong? Do I really have to plug the sensor back into the brake caliper?
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      01-30-2012, 06:14 AM   #13
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Quote:
Originally Posted by JunkStory View Post
Please help me. I recently replaced the front brake pads because they were worn, but noticed that the sensor was still untriggered. I did not buy a new sensor, but I did not want to reuse the old one either, so I wrapped the sensor portion with electric tape and zip-tied it somewhere inside the wheel well without inserting it back into the brake caliper.

I put the wheels back on, and went ahead to reset the CBS. DING! The SES and brake lights are on. What have I done wrong? Do I really have to plug the sensor back into the brake caliper?
There are two options;
deactivate the sensors with a special program
connect resistance, instead of the sensor,
in any case, better to put the new sensor, it is not expensive.
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      01-30-2012, 12:12 PM   #14
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Quote:
Originally Posted by JunkStory View Post
Please help me. I recently replaced the front brake pads because they were worn, but noticed that the sensor was still untriggered. I did not buy a new sensor, but I did not want to reuse the old one either, so I wrapped the sensor portion with electric tape and zip-tied it somewhere inside the wheel well without inserting it back into the brake caliper.

I put the wheels back on, and went ahead to reset the CBS. DING! The SES and brake lights are on. What have I done wrong? Do I really have to plug the sensor back into the brake caliper?
If the front sensors are really untriggered then the rears "are" and so you would get the warning lights. Remember that these are two stage sensors and so the first stage trigger happens long before new brakes are needed.
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      01-30-2012, 02:46 PM   #15
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I've got new F&R sensors, pad, rotors and hardware. I'm resetting the light.
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      01-30-2012, 10:39 PM   #16
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Moral of the story just spend $15 and buy a new sensor. Note: There are only 2 sensors; one for the front and one for the rear.
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      01-31-2012, 11:55 AM   #17
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^exactly.
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      01-31-2012, 11:29 PM   #18
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I have been told by BMW service that the sensors are magnetic, they probably don,t touch the disc until worn to the minimum. I have read that the sensor distorts when removed from the backplate and is not reusable. I also understand that you cannot reset the OBC if the pads are not showing more than 80% worn,

Regards,

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      10-03-2012, 10:12 AM   #19
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Got a CBS / brake pad wear sensor question:

My car is still under factory warranty. When I got my car in July, the rear brakes had 4100 miles to go. They have been steadily declining since. When I do some fast driving on twisty roads, especially if I power out of corners, the miles to go will reduce by 100 miles each time. It's the DSC using the rear brake pads as a "simulated limited slip".

The indication got down to 1000 miles to go just before last weekend. On Sunday I did the BMWCCA autocross at the Auto Club Speedway in CA. A few days later the sensor still reads 1000 miles to go. There is no way that I didn't wear out those rear brake pads that day - we did 10 practice runs and 3 timed runs and I had DTC on the whole time.

Does the CBS miles to go stop at 1000 miles until you hit the second stage of the wear indicator? I need to know in order to schedule my appointment to get my rear pads changed. I want to get a nice BMW loaner and not just some cheesy rental car.

Plus my rear brakes squeal like hell and I want that problem resolved.

Thanks!
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      10-06-2012, 07:14 AM   #20
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Quote:
Originally Posted by NoTempoLimitN54 View Post
Got a CBS / brake pad wear sensor question:

My car is still under factory warranty. When I got my car in July, the rear brakes had 4100 miles to go. They have been steadily declining since. When I do some fast driving on twisty roads, especially if I power out of corners, the miles to go will reduce by 100 miles each time. It's the DSC using the rear brake pads as a "simulated limited slip".

The indication got down to 1000 miles to go just before last weekend. On Sunday I did the BMWCCA autocross at the Auto Club Speedway in CA. A few days later the sensor still reads 1000 miles to go. There is no way that I didn't wear out those rear brake pads that day - we did 10 practice runs and 3 timed runs and I had DTC on the whole time.

Does the CBS miles to go stop at 1000 miles until you hit the second stage of the wear indicator? I need to know in order to schedule my appointment to get my rear pads changed. I want to get a nice BMW loaner and not just some cheesy rental car.

Plus my rear brakes squeal like hell and I want that problem resolved.

Thanks!
The CBS is a miles-to-go estimate of remaining pad life. Once the pad replacement indictor light comes on and stays on, the pads need to be replaced. You cannot just go by the CBS estimate.
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      11-24-2012, 10:28 PM   #21
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Quote:
Originally Posted by NoTempoLimitN54 View Post
Got a CBS / brake pad wear sensor question:

My car is still under factory warranty. When I got my car in July, the rear brakes had 4100 miles to go. They have been steadily declining since.

The indication got down to 1000 miles to go just before last weekend. On Sunday I did the BMWCCA autocross at the Auto Club Speedway in CA. A few days later the sensor still reads 1000 miles to go.

Does the CBS miles to go stop at 1000 miles until you hit the second stage of the wear indicator?
UPDATE: It turned out the rear pads had plenty of life left. But now my front pads recently went from 14000 miles to go to 1400 miles to go. I had a front wheel off the other day and I saw that the pads were worn. I'm assuming that I passed the first stage of the wear sensor.

My brake fluid change is due 1/2013. I drive about 1000 miles per month. I've got a little over 1000 miles to go to hit 50k when factory warranty expires (but I still have CPO and extended maintenance).

Is it worth it to try to get them to do the pads/rotors/fluid before I hit 50k or does it not matter having CPO and extended maintenance?
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      03-15-2013, 08:29 PM   #22
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Thank god for this thread, because w/out it I would be lost.

A while back (about 5 months ago) I replaced my front and rear brake pads, but never touched the sensors. I kept the old ones in, and yesterday I received a code CCID 41. I went through the procedure of resetting, however after the reset I received a code CCID 71 and the red "brake" light indicator along with the car on the lift.

After reading this thread I am convinced that it is indeed the brake lights sensor. Anyone know where I can purchase the sensors without going to the dealer, and 2nd how hard is it to install? I noticed that the cable is a far bit tucked in looking from underneath the car. If anyone can provide a link to the sensors I would greatly appreciate it,

thanks,
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