[Mr. Toad]

I recently took my car in for a proactive (unprompted by the CBS computer) oil change at 7,500 miles because I prefer not to let it go 15,000 or more miles without service. The SA read the key and advised that an oil change wasn't due, and I explained that I like to have it changed at about half the CBS interval. I also mentioned that the computer indicated a rear brake service in about 3,000 miles and he said they'd check the pads and rotors and let me know what they looked like.

When I got the car back, I was informed that the rear pads/rotors were in good shape and would probably last longer than the 3,000 miles suggested by the computer.

A day after this service, I pulled up the Required Service screen in iDrive and discovered that they had reset the counters for the engine oil and the front and rear brakes. The rear brakes monitor, which had indicated 3,000 miles a day ago, now shows 42,000 miles, and the front brakes monitor shows 70,000 miles, so it seems I have no way of knowing when these services should actually be performed.

I called the dealer and the SA stated that it didn't matter because the computer would still alert me at the proper interval. Is this true? Is there any way to readjust the miles/dates in the computer to reflect something closer to reality (i.e., what it showed before the reset)?

[m42stanle]

Originally Posted by rjg

I recently took my car in for a proactive (unprompted by the CBS computer) oil change at 7,500 miles because I prefer not to let it go 15,000 or more miles without service. The SA read the key and advised that an oil change wasn't due, and I explained that I like to have it changed at about half the CBS interval. I also mentioned that the computer indicated a rear brake service in about 3,000 miles and he said they'd check the pads and rotors and let me know what they looked like.

When I got the car back, I was informed that the rear pads/rotors were in good shape and would probably last longer than the 3,000 miles suggested by the computer.

A day after this service, I pulled up the Required Service screen in iDrive and discovered that they had reset the counters for the engine oil and the front and rear brakes. The rear brakes monitor, which had indicated 3,000 miles a day ago, now shows 42,000 miles, and the front brakes monitor shows 70,000 miles, so it seems I have no way of knowing when these services should actually be performed.

I called the dealer and the SA stated that it didn't matter because the computer would still alert me at the proper interval. Is this true? Is there any way to readjust the miles/dates in the computer to reflect something closer to reality (i.e., what it showed before the reset)?

Reset of CBS indicator for oil is standard practice after any oil change at least at my dealer. My last few oil changes have been low mileage (1 yr) and they always reset the indicator. I track the service by time myself so I have no issue with this.

Your dealer's reset of the CBS indicator for brake life is also normal given your complaint and it's exactly what mine did also (in my case CBS thought rear brakes were due for replacement and in reality they were not even 50% worn with 8-9mm pad remaining). CBS for brakes is notoriously unreliable for these cars especially before the first sensor has been triggered (i.e., before pads are 50% worn).

I would not stress too much about this, the CBS indicator will become a little more accurate after the first sensor is tripped around 50% wear, and as an added safeguard you will get a continuous brake warning light when the second sensor is tripped around the time the brakes are completely worn.

I also keep track of pad wear by physically measuring pad life a couple of times a year since I am taking the wheels off anyway to switch over to summers/winters. This is definitely the best way to ascertain actual wear but may not be practical for you depending on how comfortable you are jacking up the car and taking wheels off (or depending on wheel style you can sometimes peek between the spokes and get a rough measurement).

[Wilt]

Originally Posted by m42stanle

Reset of CBS indicator for oil is standard practice after any oil change at least at my dealer. My last few oil changes have been low mileage (1 yr) and they always reset the indicator.

Interesting difference, my dealer does NOT reset the oil change interval at low mileage annual service...one done in April 2014, one done in August 2015 (no microfilter either time).
When the CBS then told me in August 2014 that oil change was due, they changed oil and filter and microfilter and reset the oil service reminder.
If the tech had read and complied with the the service order instructions (in August 2015), they would NOT have reset the SI, but the tech didn't follow instructions so they reset it after all! So I am now 13000 miles from my next microfilter, theoretically, which is about 1.4 years away at the rate I accumulate miles.

The CBS being so far off is of little consequence, it is a 'guess' based upon your driving habits. Pay attention to mechanic status reports on pad thickness based upon visual inspection...below 5mm you are getting close to needing pads. And the sensor will absolutely tell you 'get pads now' with a warning light.

[Mr. Toad]

Originally Posted by Wilt

Interesting difference, my dealer does NOT reset the oil change interval at low mileage annual service

Historically, mine has never done this either. I've always worked with the same SA, and he has never reset after a non-prompted oil change. This time, however, he was out and I was assigned to another SA whom I've never worked with before. My regular SA would definitely not have reset the CBS.

Originally Posted by Wilt

the sensor will absolutely tell you 'get pads now' with a warning light.

Are there two different warning lights for brake service - one for "service approaching" and another for "service due NOW"?

[WordOnRoad]

Why wouldn't you want your CBS data corrected to reflect proper service intervals...

[m42stanle]

Originally Posted by rjg

Historically, mine has never done this either. I've always worked with the same SA, and he has never reset after a non-prompted oil change. This time, however, he was out and I was assigned to another SA whom I've never worked with before. My regular SA would definitely not have reset the CBS.

OK I didn't realize other dealers were handling this differently, could be it's a US/Canada difference? Maybe I am missing something here but I am still not seeing a problem - BMW specifies cabin filter change at every second oil service in either case. In a low mileage car if the indicator was never reset you could be going 3-4+ yrs without replacing cabin filter which I don't think I would want. If they reset CBS at each oil service for that same car (i.e., once per year) in worst case you would change cabin filter every two years (I change it once per year but that is mainly because of driving conditions & because I do microfilter myself).

Originally Posted by rjg

Are there two different warning lights for brake service - one for "service approaching" and another for "service due NOW"?

Yep, CBS for brakes is a two sensor system, first is triggered around the time brakes are 50% worn (which helps CBS better gauge wear from that point forward, but no warning light is illuminated) and a second which when tripped will light up the a brake warning light which will stay on until you replace the sensor & reset CBS. There are a few other threads on here that explain CBS for brakes in really good detail.

[robthewrench]

Originally Posted by m42stanle

Yep, CBS for brakes is a two sensor system, first is triggered around the time brakes are 50% worn (which helps CBS better gauge wear from that point forward, but no warning light is illuminated) and a second which when tripped will light up the a brake warning light which will stay on until you replace the sensor & reset CBS. There are a few other threads on here that explain CBS for brakes in really good detail.

+1. You should really ignore the projected service interval for the brakes and just wait for the service now sensor to be tripped. When this does get tripped you've got ~1000 miles before you are grinding pads / rotors and have a braking system problem.

My projected service interval for the rear brakes has been 3100 miles for the past year. The pads have more than this left on them, so somehow when the dealer changed the pads, the old sensor was re-used, or something.

[Mr. Toad]

Originally Posted by m42stanle

OK I didn't realize other dealers were handling this differently, could be it's a US/Canada difference?

Originally Posted by m42stanle

Maybe I am missing something here but I am still not seeing a problem

According to my regular SA, CBS should not be reset when the oil is changed "off schedule" because it is tied to other services that are performed based on the number of oil changes as prompted by the computer (so an unprompted service should not be allowed to interfere with the computer's calculations). I seem to recall him mentioning something about spark plugs, as an example, but I may be wrong.

Originally Posted by m42stanle

CBS for brakes is a two sensor system, first is triggered around the time brakes are 50% worn (which helps CBS better gauge wear from that point forward, but no warning light is illuminated) and a second which when tripped will light up the a brake warning light which will stay on until you replace the sensor & reset CBS.

When you say that the "first [brake sensor] is triggered around the time brakes are 50% worn", are you referring to something the car only communicates to itself ("no warning light is illuminated")? If so, this would not help the driver know when a service need is approaching. Is my car now only going to alert me when brake service is required immediately? I would prefer some advance notice.

Thanks for your help!

[Efthreeoh]

I just don't understand the difficulty of people understanding how the brake pads monitor works. The front left and right rear brake have sensors. The sensors are consumables. The sensors are dual-stage that is needed to estimate the rate at which the pads are consumed. This determines the estimate of remaining pad life in mileage. But in the end, the system tells the driver when the pads need replacement. All you need to do is wait until the notification shows up in the gauge cluster.