"check brake linings" gremlin

[jicaino]

Hey! My 540i has developed a gremlin: the "check brake linings" OBC message. Both cables are good and new, as pads. I checked the connection boxes and discovered the fron left one sort of undone (no lose connectors inside, but still, the plastic cage that holds the wheel sensor and the brake pad connectors was partially open)

Any ideas as to where can I keep on searching for stuff gone wrong?

- - - Updated - - -

EDIT: happens mostly when hot (as in mid/high speed driving with lots of braking, or lots of braking in stop and go)

[mattmar1]

i did once have the same thing happen, found one of the wires connected to the chassis connector cracked at the connector to the pin. the plastic housing had broken, allowing the connector to move around cracking the wire. a bit of soldering fixed it.

[CSMBlack-540i]

Probably continuity issue somewhere since plastic cage probably let water into connections for some time. If possible, check continuity and/or resistance of wiring.

[Chedley]

Check and grease all your braking system : brake fluid level, pads thikness, rotors, calipers, etc....
If all is well, just disconnect that "idiot sensor" --front and rear pad wear sensor-- , then reset and turn off the OBC message "

"check brake linings".

[mattmar1]

if you disconnect the wear sensor, its the same as an open sensor, which will trigger the lite. the connection has to be a closed circuit to disable the light.

[Chedley]

if you disconnect the wear sensor, its the same as an open sensor, which will trigger the lite. the connection has to be a closed circuit to disable the light.

Right. I mean you disconnect it from the brake pad.

Disconnect the wear sensor's termination from the brake pad, but keep it connected to the car. Roll it and tape it around the suspension arm so it will not be hanging loose.
No more red light, as its circuit stays closed, even when the brake pads get real thin -below 3 mm I think-.

[BimmrMeUpSnotty]

You bunch of hacks.... OP, check for continuity, there is a frayed wire, and replace the wires. Don’t be a hack...

[jicaino]

You bunch of hacks.... OP, check for continuity, there is a frayed wire, and replace the wires. Don’t be a hack...

Don't worry, I wasn't going to start yanking things off. When I choose to deactivate a certain feature I remove all the stuff using OEM plugs, covers and caps, and code them out. Like when I ditched intensive washing, and headlights washers because I have halogen and it's pretty much useless unless you want to use that for fouling your entire car-

I'll chase the bug and kill it with the proper venom.

[ross1]

Check and grease all your braking system : brake fluid level, pads thikness, rotors, calipers, etc....
If all is well, just disconnect that "idiot sensor" --front and rear pad wear sensor-- , then reset and turn off the OBC message "

"check brake linings".

This is terrible advice. There is no "reset" other than correcting the problem or defeating the wear sensor.
OP has an intermittent open circuit, most likely at one the connections* or a sensor that is not quite worn through yet.
* The pins are very tiny and sometimes will entirely melt away in corrosive environments.

[Santaclaus4]

You bunch of hacks.... OP, check for continuity, there is a frayed wire, and replace the wires. Don’t be a hack...

What's with all the sugarcoating?! Your getting soft...

[jicaino]

This is terrible advice. There is no "reset" other than correcting the problem or defeating the wear sensor.
OP has an intermittent open circuit, most likely at one the connections* or a sensor that is not quite worn through yet.
* The pins are very tiny and sometimes will entirely melt away in corrosive environments.

I know, don't worry. I thought the same, what if a newcomer asks for this, it would be directed to botch and butcher an useful feature. Not to mention I stated I've recently done brakes and checked for wear/mishaps.
I'd probably start by swapping out the front pad sensor which was the one whose retaining cage was open, and I think the pad clip was a tad on the "loose" side.

What's with all the sugarcoating?! Your getting soft...

[BimmrMeUpSnotty]

What's with all the sugarcoating?! Your getting soft...

Nah, not getting soft, just sick and tired of apologizing to JimboLevster for hurting all these noobsterz softy f'kin feelings. Of course, I am getting quite bored seeing all these broken record threads, these twits chime in with their ten cents of bad advice, so every now and then..... We'll shet, I gotta hold back....., yeah.... I've gone soft.... These f'kin weak feeling'd bunch of sorry assed pansies.... pisses me off, we gotta breathe the same f'kin air these little ding dongs breathe.... Thanks SandyKlaus, now I gotta go f'kin apologize to JL again, you f'kin happy?

[JimLev]

LOL, good reply Snotty.
I'm just trying to keep you off another 3 month forced "vacation". Most of us here enjoy your posts, I sure do.
I've always gone by the rule if you don't know what your talking 'bout Keep your pie hole shut.

[BimmrMeUpSnotty]

Haha! Glad you saw the humor in that post, I was laughing when I typed it up.

[JimLev]

As much as I'd like to lay some crap on some of the replies I read I gotta hold back.
I do get to send peeps on vacation.

[StephenVA]

ha ha!

[Santaclaus4]

Nah, not getting soft, just sick and tired of apologizing to JimboLevster for hurting all these noobsterz softy f'kin feelings. Thanks SandyKlaus, now I gotta go f'kin apologize to JL again, you f'kin happy?

I'm laughing so hard I'm almost in tears...

[BimmrMeUpSnotty]

I'm laughing so hard I'm almost in tears...

Laughter is life’s best medicine, glad to be of service, the bills in the mail.

[Chedley]

Alright...Assuming the problem is with the sensor.
Do we really need a sensor that triggers a red light when the brake pads are down to less than 3 mm...?? Can't we see the thikness of the pads visually, without even removing the tires to inspect the brakes ??

You really don't no pad sensor.

Cut the wires on the pad sensor then connect the wires together and roll them back into that plastic cage box-. That closes the circuit, turns off the red "check brake linings" light,...and -those pad "idiot-sensors" will never be heard from again--.

[Spirit Force]

Check and grease all your braking system : brake fluid level, pads thikness, rotors, calipers, etc....
If all is well, just disconnect that "idiot sensor" --front and rear pad wear sensor-- , then reset and turn off the OBC message "

"check brake linings".

I gotta ask, do you have any clue what you are talking about? Greasing everything ain't gonna fix it. The only way to fix it is to find out the issue. This means OP needs to check the wiring for continuity. If everything was well there wouldn't be a light in the first place. Besides you can't see the pad thickness without removing the wheel (the inside pad, which you should always check). You do realize the inside pad wears more quickly than the outside pad with one piston caliper? You won't be able to check the inside pad thickness without removing the wheel on E39.

[StephenVA]

Brake Pad thickness - How to measure correctly
The factory tool for checking brake pad thickness.

Found a time saving special brake tool that might be new to some of us.
Baum Tools - brake thickness measurement tool. No need to remove the wheel, just insert the tip into the back of the brake pad through the wheel and see the measument in MM. Yes, it is pricy but it beats the heck out of pulling multiple wheels on my stable of of BMWs. 5 mins of effort beats pulling wheels each quarter. Those of you who do this for a living already own one I am sure. It was new to me and after seeing one in action, I added it to my Christmas list and ordered it!
Multiple tool vendors sell it, all at the same $$$ ($89. USD). Welcome to special tools...
For gauging brake lining thickness w/o wheel removal, PN: 341260
Tool Listing: Tool Listing


Info is on the Baum website.
To buy http://www.toolsource.com/brake-gauge-p-104624.html

Note: This only measures the outside pad thickness, As mentioned previously the inside pad wears 2-10% faster (especially if the calipers are not receiving annual cleaning and lubing of the contact points) Gee I do this. Don't you all?

[jicaino]

Alright...Assuming the problem is with the sensor.
Do we really need a sensor that triggers a red light when the brake pads are down to less than 3 mm...?? Can't we see the thikness of the pads visually, without even removing the tires to inspect the brakes ??

You really don't no pad sensor.

Cut the wires on the pad sensor then connect the wires together and roll them back into that plastic cage box-. That closes the circuit, turns off the red "check brake linings" light,...and -those pad "idiot-sensors" will never be heard from again--.

The pad sensor wires aren't a continuity trigger. If you stick them together you'll still trigger a fault. You need to do some actual reading instead of laying a steaming pile of BS on every thread, you might end up confusing the less experiencied E39'er here, in addition to annoying the seasoned ones.

[ross1]

The pad sensor wires aren't a continuity trigger. If you stick them together you'll still trigger a fault. You need to do some actual reading instead of laying a steaming pile of BS on every thread, you might end up confusing the less experiencied E39'er here, in addition to annoying the seasoned ones.

When the sensor wears through it opens the circuit. Splicing the wires DOES effectively defeat the sensor.

[jicaino]

When the sensor wears through it opens the circuit. Splicing the wires DOES effectively defeat the sensor.

Have you done so? I have and it doesn't work that way. Seems to me Chedley just got a BS assistant.

[mattmar1]

When the sensor wears through it opens the circuit. Splicing the wires DOES effectively defeat the sensor.

agree with this completely. the pad sensor is a metal "loop", when the pad thickness get down to a certain level, it breaks, opening the circuit and triggering the light.