[MountainStone]

Just had both rear wheel bearings replaced, along with both hubs and an axle. While the shop had the rear end disassembled they installed new OEM brake pads at no additional labor charge (old pads were at about 25% remaining).

When I retrieved the car from my Indy, he related some bad news: the 'brake' light is on, the center screen shows the red 'car on a lift' icon and the iDrive screen states the brakes are worn to minimum thickness, visit workshop.

He says they used a new sensor for the rear and they never touched the front of the car until the warning appeared, then they checked the front brakes which are still at 75% remaining. He is not surprised the code set since they disassembled the rear of the car and disconnected the pad wear sensor, but he is unable to get the car to reset the brake warning.

He tells me I am the 4th person to have this exact phenomenon happen and it is due to the JB4. He stated if I remove the JB4 and bring it back to him, he can hook up to the car and code the warning back to normal. He swears he's done this on three other cars.

When i got home I set the JB4 to map 0 via the steering wheel controls then attempted to reset the service reminder. I was unsuccessful. When viewing both front and rear brake icons in the cluster, the miles remaining shows only '......' This is very odd as there should be numbers there. I'm stumped.

Does this sound familiar to anyone? Anybody have an idea I can try before removing the JB4 and leaving the car with the shop for another day? Seems like a weird and super-annoying bug if accurate.

[naynay]

1. remove the brake sensor.
2. make a short between the two prongs from the brake sensor.
3. reset the service light.
4. reconnect your stock sensor.

you can use the mother board power pins. grab two. cut the wires, tie them up and connect it to your brake sensor connector. the car reads the ohms from the brake sensor it self. when you change it, it gives you a differnt value, when you short it. it tricks the car into thinking that you've replaced them. once reset you can put the old one back on.

[MountainStone]

Thanks, I'll try that.

[lichtgelb]

I fixed this same problem last night. I had unplugged my sensors for other work and when I put everything back together I had the same red light and car on a lift warning. I plan on doing a complete brake job in the near future so for now I just bought some new sensors and tied them up in the wheel wells. After hooking up the new sensors I had to do a brake pad sensor reset in the service reset menu. You enter this by holding down the small button on the instrument cluster with the ignition on for three seconds...wait for all the initial messages to clear before pushing the button. Once a triangle with an exclamation point comes up you can use the BC button to select the brake pads and reset them.

[techwhiz]

Originally Posted by naynay

1. remove the brake sensor.
2. make a short between the two prongs from the brake sensor.
3. reset the service light.
4. reconnect your stock sensor.

you can use the mother board power pins. grab two. cut the wires, tie them up and connect it to your brake sensor connector. the car reads the ohms from the brake sensor it self. when you change it, it gives you a differnt value, when you short it. it tricks the car into thinking that you've replaced them. once reset you can put the old one back on.

Yep, you can't reset with an old sensor.
You either need a new sensor or short the pins.

[MountainStone]

I got it fixed thanks to the advice in this thread.

As instructed, I disconnected the rear wear sensor and placed a jumper wire across the terminals. Then I was able to reset the warning in the instrument cluster normally. After the reset I re-connected the wear sensor and checked again; warning is gone.

Thanks everybody!

[PhaseP]

He says they used a new sensor for the rear

If you were able to reset with shorting like that, it means they reused the old sensor, didn't put a new one. New one will be short circuit, until it wears down to first stage, it goes to 470 ohms. Then at last stage which you get light to replace the break it is open circuit. They may not be experienced with e90 sensors. Earlier BMW brake sensors are two stage, short circuit or open circuit, and they only need replacement if they tripped to open circuit. E90 2 stage sensors need replacement even if they reached the 1st stage, which will be most often the case.

You have a sensor there now at 470 ohms, 1st stage tripped.

Your brake pad estimated remaining miles in your CBS computer will be off because computer will now thinks in a short time you got from new sensor to 1st stage off, but that is no big deal. The important one is not the CBS estimate miles, but the red light on the dash which is the accurate indicator for time to replace the pads.

[MountainStone]

You are correct that they did not replace the sensor, I confirmed that when I disconnected it. I checked my bill and there is no charge for a new sensor, I'm not sure why I thought they replaced it. I find it curious the sensor had worn into the first stage but the car never notified me of impending brake pad replacement; does the computer only use the input to calculate miles remaining (which I never check)? You're correct that the estimated remaining miles only shows 11000 miles remaining. Will the computer warn me to change the pads in 11000 miles? Maybe I should install a new sensor...

Thanks for the education by the way!

[PhaseP]

does the computer only use the input to calculate miles remaining

Yes, it doesn't notify user about it, it happens somewhere in the middle of the life of the pad.

After a reset computer seems to be very pessimistic, even with a brand new sensor. Then as it monitors the usage it keeps readjusting its estimate. So you probably will get later than 11Kmiles warning to replace, don't know how much longer.

Maybe I should install a new sensor...

I guess so, it is less headache overall to replace the sensors each time with new pads and reset the computer for that axle. They are not very expensive neither, nor difficult to replace.