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I have a 2012 328i. My brake light and car on a hydraulic lift light came on. I took car to a dealer and they checked the brake pads and still have about 60% remaining. They tried resetting the warning light and light would not go out. They hooked up on their computer and it indicated a rear brake fault. They tried replacing the rear sensor and light still on. So brake pads and sensors are not the problem. They are puzzled. They need me to bring car back and leave it for further diagnosis.

Does anyone have any clue what this might be?
 

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That is an interesting thought. Don***8217;t you think the technicians computer would pick that up if the fluids were low? It is showing a rear brake default code on their diagnostic computer they use.
 

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What code does it have? What reset procedure did they use? Did they reset the wear timer AFTER they replaced the wear sensor?
 

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I have a 2012 328i. My brake light and car on a hydraulic lift light came on. I took car to a dealer and they checked the brake pads and still have about 60% remaining. They tried resetting the warning light and light would not go out. They hooked up on their computer and it indicated a rear brake fault. They tried replacing the rear sensor and light still on.
The red BRAKE warning indicator on the upper cluster, and the "Car on Lift" in the middle cluster indicate failed/worn brake pad wear sensor, OR a fault in the sensor wiring, connectors or circuit. Those two indicators light IF the circuit goes open-circuit, as sensed at the DSC under the hood per this installation location:
https://www.newtis.info/tisv2/a/en/e90-328i-lim/RJPFfg1

As you can see from the following TIS circuit diagram for the Brake Pad Wear Sensors (B17a rear, and B16a front) there are two wires that go from the DSC module (A65a) to the Rear Brake Pad Wear Sensor (B17a), and those two wires are Yellow/Black (positive voltage) and Black Yellow (Ground):
https://www.newtis.info/tisv2/a/en/...ction-control-system/sensor-system/1VnXnOgRAD

AFAIK, INPA & ISTA (Dealer level diagnostic software) will ONLY tell you if there is an open circuit in the front pad wear sensor circuit, or Rear pad wear sensor circuit. It will NOT tell you exactly where the fault or open circuit is in either of those circuits, other than identifying which of the two circuits is faulty, so you have to test the wiring the "old fashioned way" with a continuity tester (ohmmeter ;-). That is at least all my version of INPA is able to do.

To test the system, locate the pad wear sensor at the right rear wheel, inboard pad, and follow the wiring from that sensor inboard & upward to a connector mounted to the chassis (beside the RR wheel ABS wheel speed sensor connector). Disconnect the sensor at the Connector to the Chassis (X18146 in the Schematic above) and put a "jumper" such as a paper clip into the two sockets shown in this "Connector View" so as to complete the chassis side of the circuit
https://www.newtis.info/tisv2/a/en/e90-328i-lim/HRJBHSti

Try to reset the CBS (Condition Based Service) Rear Brake Service (pad replacement) reset. If you CANNOT reset and turn the warning lights off doing that, with the jumper in place, then there is a fault on one of those two wires going forward to the DSC, and each separate wire needs to be tested for continuity, the break or open circuit repaired, and CBS reset successfully completed to make the warning lights go out.

If you have a multimeter & some patch cable/ wire, you can do all that testing yourself, and spare the cost & inconvenience of dealing with the dealer. :) Here is the "Connector View" for Connector X18303 at the DSC on OLDER models. There may be some difficulty finding proper documentation of your connector and how to access it, so check TIS for your model. Many connectors have TINY numbers next to some of the sockets, and of course you are looking for Yellow/Black wire at Pin/Socket #40 & Black/Yellow wire at Pin #21:
https://www.newtis.info/tisv2/a/en/e90-328i-lim/CTMTTUFx

Please let us know what you find,
George
 

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Thank you for your detailed explanation of what needs to be tested. I will share with my tech. I understand in concept what you explained and I recall my tech mentioning that there must be a break somewhere in the circuit but not something he had seen before and he***8217;s a veteran tech with 22 years. I was hoping others in this forum experienced a similar default and could point to a specific problem. Thank you again.
 
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