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      07-26-2021, 11:23 AM   #1
rjn
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Front brake pad light?

Had a brake light warning come on last night - keep reading please

Car is a 2107 OGM2, with 22K miles, aftermarket street pads, with the wear sensors removed, and zip tied out of the way (to support easy track pad use)

Says to drive moderately and replace front pads. What?!

I know these street pads are thick. So I reset the light, making a note to see if the pad wear sensor wire rubbed through or something. The light goes out. Car drives and brakes fine. Couple days later, the light comes on again.

So today I jack it up, and confirm that both inboard and outboard pads are VERY meaty, the wear sensor is still nicely zip tied out of the way, and also that the brake fluid reservoir is fully topped up.

Question is what could this be? I'll try the reset one more time, but in my many years of BMW experience, there's usually something pretty elemental driving this. Car's out of warranty, and I've eyeballed all the parts. I'm at a loss of what else to check.

Anyone BTDT?
Thanks for your thoughts,
Rob
17 M2

Last edited by rjn; 07-26-2021 at 12:04 PM..
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      07-26-2021, 11:28 AM   #2
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Could the sensor do this if it were dirty?
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      07-26-2021, 12:03 PM   #3
rjn
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Not likely - It's a wire that sends a fault by opening a circuit when the rotor abraids through it.
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      07-26-2021, 12:09 PM   #4
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Couple things to check. Wire could be broken within the sheething due to vibration or cycling bending where it’s zip tied. Also check the plug where the sensor plugs in (they are replaceable), so unplug sensor and test it for continuity. Could also corrode in the plug (haven’t seen that myself, but possible).
These things signal the computer that the pads are toast when the pad wears down far enough that the little sensor burns through and the circuit opens. Then bmw replaces the pads and the wear sensor.
I’ve also zip tied mine up out of the way since I’m watching my pads closely as I have wheels off a lot.
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      07-26-2021, 08:28 PM   #5
rjn
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DTH - Thanks. Sometimes I need to hear it to be reminded.

Took out the sensor wire and ran it through the ohm meter - open.

Which is what I initially suspected, but really surprised the sensor wire failed thoughtfully tied away fro the the rotor and caliper assembly - I mean this thing is designed to operate for thousands of miles at brake pad operating temps, right?

Shorted the junction at the connector, put things back together, and all is well so far. Good to know it's still super simple fault logic.

Thanks again for the fresh eyes perspective,
Rob

Last edited by rjn; 07-27-2021 at 01:59 PM..
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