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  #1  
Old 08-12-2019, 11:36 AM
robmaxfli robmaxfli is offline
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Yellow Brake Warning light is on

2008 X# - I checked both front and rear pads and they are almost like new. I ran ISTA to see if I could narrow this down but no codes related to brakes. I cleared all of the codes anyways and then the dash light went off. But 2 weeks later the light came back on.
Any advise on how to t-shoot this?

thanks
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  #2  
Old 08-12-2019, 12:02 PM
timarnold timarnold is offline
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Did you check the level of your brake fluid?
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  #3  
Old 08-12-2019, 04:09 PM
robmaxfli robmaxfli is offline
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yes - i should have mentioned that.
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  #4  
Old 08-12-2019, 05:04 PM
dukedkt442 dukedkt442 is online now
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Yellow Brake Warning light is on

Did any exceptionally heave braking happen to precede the light?

Yellow “brake” lit up, or the circle with the “!” In it?

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Last edited by dukedkt442; 08-12-2019 at 05:29 PM.
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  #5  
Old 08-12-2019, 05:18 PM
BMWaufKS BMWaufKS is offline
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Which light illuminates for a bad brake light bulb? Seems as if it wouldn't have cleared, though.
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Since 1/2016, restoring a
2008 BMW X3 M-Sport, N52, automatic ("#1")
Modifications:
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Since 3/2017, also restoring a
2008 BMW X3 base-model, N52, automatic ("#2")
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  #6  
Old 08-13-2019, 09:26 AM
robmaxfli robmaxfli is offline
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Its the round one on the dash that is next to the "BRAKE" light.

Last edited by robmaxfli; 08-13-2019 at 09:38 AM.
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  #7  
Old 08-13-2019, 02:37 PM
DangermouseX3 DangermouseX3 is offline
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I would pull out the pad sensors and inspect them and also the connectors. If the pads have meat on them, then work backwards.
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  #8  
Old 08-16-2019, 03:39 PM
robmaxfli robmaxfli is offline
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I checked all the pads, the fluid level, the brake light bulbs - then changed both the front and rear pad wear sensors - but that pesky dash light is still on....
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  #9  
Old 08-16-2019, 06:32 PM
BMWaufKS BMWaufKS is offline
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What code scanner / eraser are you using?
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-------------------------------------------------
Since 1/2016, restoring a
2008 BMW X3 M-Sport, N52, automatic ("#1")
Modifications:
All stock except dashcam

Since 3/2017, also restoring a
2008 BMW X3 base-model, N52, automatic ("#2")
Modifications:
Dashcam, cargo cover, cargo mat
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  #10  
Old 08-16-2019, 07:28 PM
robmaxfli robmaxfli is offline
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Ista +
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  #11  
Old 08-16-2019, 07:49 PM
BMWaufKS BMWaufKS is offline
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Parking brake seem to engage/disengage normally? Is there a sensor on it that's maybe bad or needs adjusting?

These things have any mileage or time counter for demanding a brake fluid change? Or some way for it to tell if the wrong fluid was used?

Also, of course with any weird electrical problems, are the battery and cable-ends good, and ground straps been replaced?
__________________
-------------------------------------------------
Since 1/2016, restoring a
2008 BMW X3 M-Sport, N52, automatic ("#1")
Modifications:
All stock except dashcam

Since 3/2017, also restoring a
2008 BMW X3 base-model, N52, automatic ("#2")
Modifications:
Dashcam, cargo cover, cargo mat
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  #12  
Old 08-17-2019, 11:47 AM
ac_2007 ac_2007 is offline
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BMW Scanner 1.4 should tell you why that light is on. Give it a try.
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  #13  
Old 08-17-2019, 01:20 PM
robmaxfli robmaxfli is offline
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I found this article on brake pad sensor testing:

https://www.pelicanparts.com/techart...or_Testing.htm

I am showing a correct 4.5V on both sensors but the article states that I should be showing close to 0 V for the ground wire. I am showing -4.5V for the ground wire on both sensors (instead of 0).

In the last step of the testing article it states "If you are missing a ground, you can simply add a ground at terminal 2 at the front or terminal 1 at the rear to test your theory."

I want to try this but I am not sure how to physically do this. How would I add a ground wire and where would I connect it?

thanks
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  #14  
Old 08-17-2019, 04:30 PM
dukedkt442 dukedkt442 is online now
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Sounds like you have a short allowing current to reverse. Did you test each sensor harness for resistance? To jump a ground, just take a jumper wire with an alligator clips, clip it to the respective terminal, and the other end do the chassis. Without clips, just hold a wire in place. The pad wear wire needs to be disconnected from the sensor harness, which is where you are doing your work. The pelican page has the pictures.

Edit: are you measuring voltage across terminals 1 & 2, and then reversing your probes to measure the other terminal? If so, that is why the voltage is mirrored but reversed. Connect one lead to the terminal, the other to the chassis.
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Last edited by dukedkt442; 08-17-2019 at 04:43 PM.
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  #15  
Old 08-17-2019, 05:12 PM
robmaxfli robmaxfli is offline
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Quote:
Originally Posted by dukedkt442 View Post
Sounds like you have a short allowing current to reverse. Did you test each sensor harness for resistance? To jump a ground, just take a jumper wire with an alligator clips, clip it to the respective terminal, and the other end do the chassis. Without clips, just hold a wire in place. The pad wear wire needs to be disconnected from the sensor harness, which is where you are doing your work. The pelican page has the pictures.

Edit: are you measuring voltage across terminals 1 & 2, and then reversing your probes to measure the other terminal? If so, that is why the voltage is mirrored but reversed. Connect one lead to the terminal, the other to the chassis.

Yes - you are correct - that is why I had a mirrored voltage. I understand now.

FYI - i found a you tube video that shows someone just turn their key to the run position and leave it there for a minute. The brake pad sensor light turned off. So I tried it myself - the light went out. Will this fix last ? We will see.

thanks
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  #16  
Old 08-17-2019, 05:41 PM
dukedkt442 dukedkt442 is online now
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Quote:
Originally Posted by robmaxfli View Post
Yes - you are correct - that is why I had a mirrored voltage. I understand now.

FYI - i found a you tube video that shows someone just turn their key to the run position and leave it there for a minute. The brake pad sensor light turned off. So I tried it myself - the light went out. Will this fix last ? We will see.

thanks
Sometimes just a cleaning and application of dielectric grease on the sensor plug is all that is needed; I had to replace my front sensor wire IIRC when replacing the thrust arm bushings as the wire got tugged slightly at some point in the process, resulting in the light. I'd unplug them, spray some terminal cleaner at them, and a dab of dielectric on the plug end.
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Last edited by dukedkt442; 08-17-2019 at 05:43 PM.
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