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General E46 Forum
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Old 07-08-2017, 11:48 PM   #1
ahgu
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brake yellow light and DSC light on

2004 330CI convertible.

yellow brake light and yellow DSC light ON.
Front brake pressure high.

what does that mean? I noticed the brake pads are thin. Wear sensor might be worn out.
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Old 07-09-2017, 10:49 PM   #2
Greg330CI
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Sounds to me like your brake pads are worn and need replacing. Either front, rear or both. The wear sensor(s) activate when the thickness of the pad is such that the wear sensor touches the rotor. If you continue to drive like that then eventually the metal base of the pad will contact the rotor. (ouch!) When ever I replace the pads, I replace the rotors and wear sensors. The rotors wear and end up with uneven ridges.. Although they can be skimmed flat again, it makes them thinner and prone to warping if they get really hot.

Pad replacement is quite an easy DIY but if you are unsure or don't have the tools, take it to a good indy mechanic. Good luck.
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Old 07-09-2017, 11:29 PM   #3
ahgu
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scan says:
Pressure, front-axle brake circuit 73.2 bar
even when brake is not pressed. Is that caused by worn pad sensor?

Pressure, rear-axle brake circuit -1.3 bar
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Old 07-10-2017, 12:08 AM   #4
Greg330CI
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The brake pad wear sensor is located in the actual brake pad and is simply a contact which when the pads are worn thin, comes into contact with the brake rotor and causes a circuit to close, which activates the brake wear sensor and turns on the warning light. It also logs into the diagnostic system. There are also 2 brake pressure sensors situated in the brake master cylinder. I believe one for the front and one for the rear circuits. It is this which is giving you the pressure reading. Could be that the pressure sensor itself is faulty. Do you know what the correct pressure readings should be?
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Old 07-17-2017, 01:27 PM   #5
ahgu
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I changed all 4 pads and brake sensor, the DSC and brake yellow light are still on.
Anyone has experience on this? Is it faulty pressure sensor, or the whole DSC has issue?
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Old 07-18-2017, 09:41 PM   #6
Greg330CI
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It sounds as though you have a faulty pressure sensor. However, before you replace the pressure sensor, I read that the symptoms you describe can be caused by corrosion on the contacts on the wiring harness connector that is located on the brake master cylinder that connects to the sensors. It was recommended that you remove / replace this a few times to "clean the contacts and this can eliminate the warning light symptom. Only do this with the ignition switched fully off otherwise you may cause another problem. If that does not make any difference then it is probably the sensor. Do your brakes work OK?
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Old 07-18-2017, 11:08 PM   #7
ahgu
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Brakes okay, everything normal.
Are you talking about the connector ON the pressure sensor?

How do I reach that connector? what do I have take off? Do I need to drain the brake fluid? If yes, how do I do that?






Quote:
Originally Posted by Greg330CI View Post
It sounds as though you have a faulty pressure sensor. However, before you replace the pressure sensor, I read that the symptoms you describe can be caused by corrosion on the contacts on the wiring harness connector that is located on the brake master cylinder that connects to the sensors. It was recommended that you remove / replace this a few times to "clean the contacts and this can eliminate the warning light symptom. Only do this with the ignition switched fully off otherwise you may cause another problem. If that does not make any difference then it is probably the sensor. Do your brakes work OK?
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Old 07-18-2017, 11:32 PM   #8
Greg330CI
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Take a look at this U Tube.

There are several U Tube videos here that will help you to see where the connections are. Also, if you Google BMW E46 Brake Pressure Sensor you will find additional information. The U Tube video describes your symptoms exactly including the high pressure reading on sensor 1, which I believe is connected to the DSC. Let the video run on as there are 2 related videos. Good luck!
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Old 07-18-2017, 11:33 PM   #9
Greg330CI
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Old 07-18-2017, 11:40 PM   #10
Silverdogz
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Looks like the front brake pressure sensor died on ya. Easy enough fix.
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