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BMW 3-Series (E90 E92) Forum > BMW E90/E92/E93 3-series General Forums > General E90 Sedan / E91 Wagon / E92 Coupe / E93 Cabrio > Brake (red) warning light on the dash



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      02-10-2016, 10:50 PM   #1
RL325xi
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Brake (red) warning light on the dash

Car: 2011
model : 328i
Miles: 41k
Auto

Brake warning light was on.




Took the wheels off and checked. All pads looks good.
So I tried to reset the brake light.
After I reset it,
the warning light remains



Any comment on how to address it?
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      02-10-2016, 11:05 PM   #2
shuaige
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Uh, isn't that the emergency brake light?
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      02-10-2016, 11:14 PM   #3
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its on with the engine running ? what does CBS say you have left on the brakes ?

did the sensor fall out of the pad and short against the wheel ?

How was the inside pad where they are measured (front left and right rear)

If one says 0 miles left on CBS you should concentrate on that wheel whether its the l/f or r/r
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      02-10-2016, 11:50 PM   #4
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Am I understanding this correctly...but I thought this is just your handbrake? My "red brake" light comes on when I engage the handbrake
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      02-10-2016, 11:50 PM   #5
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When the break wear indicator illuminates and stays on while the car is running it means the pads have reached the minimum thickness and need to be replaced. Visual inspection will show some remaining pad left, but it just means the pads are at a minimum. If you don't actually measure the pads you may think the pads still have life in them, but they don't. I'm reasonably sure one or both axles need new brakes.
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      02-11-2016, 12:27 AM   #6
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That seems to be the handbrake light rather than the brake pad indicator
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      02-11-2016, 12:31 AM   #7
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I'm dealing with the same thing right now. Personal inspection shows plenty of pad left. Took car to my Indy shop for professional opinion and was told that pads are only worn half way. I've got 50% left. The problem is the pad wear sensor. The sensor has to be replaced before the light will go off. Even if you reset the service light. Not sure how much truth there is in this but I was told that the sensors are designed to show more wear than necessary because when the car is under warranty the stealership wants to just replace the pads and not the rotors. So if you let the pads get too low then you jeopardize wearing grooves in the rotors thus causing the need for replacement.
I'm thinking I'll just replace the sensor and reset the service and give myself another 5k miles before considering new pads and rotors.
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      02-11-2016, 12:35 AM   #8
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Thanks all for the ideas.
To Clarify, that light stayed on even my hand brake was released
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      02-11-2016, 12:43 AM   #9
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car needs pads mine is on too doing mine soon and yes it lights up the same light as the parking brake
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      02-11-2016, 12:45 AM   #10
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Just push the damn handbrake down
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      02-11-2016, 02:55 AM   #11
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Quote:
Originally Posted by RobertRichy View Post
I'm dealing with the same thing right now. Personal inspection shows plenty of pad left. Took car to my Indy shop for professional opinion and was told that pads are only worn half way. I've got 50% left. The problem is the pad wear sensor. The sensor has to be replaced before the light will go off. Even if you reset the service light. Not sure how much truth there is in this but I was told that the sensors are designed to show more wear than necessary because when the car is under warranty the stealership wants to just replace the pads and not the rotors. So if you let the pads get too low then you jeopardize wearing grooves in the rotors thus causing the need for replacement.
I'm thinking I'll just replace the sensor and reset the service and give myself another 5k miles before considering new pads and rotors.
Robertrichy,

I think I will do the same. I will replace both front and back sensor. and hopefully, it will allow me to reset and turn off the brake warning light.

will report here once I replace them.

Thanks all
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      02-11-2016, 03:58 AM   #12
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Quote:
Originally Posted by RL325xi View Post
Robertrichy,

I think I will do the same. I will replace both front and back sensor. and hopefully, it will allow me to reset and turn off the brake warning light.

will report here once I replace them.

Thanks all
Just plug in the new sensor and reset, then go back to the old sensor. People also do this by shorting the two wires together instead of a new sensor.

If you use the new sensor with worn pads, all you're going to do is just crush/break the new sensor when you apply the brakes.
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      02-11-2016, 06:16 AM   #13
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I just remember that dealerships won't even replace pads until they're reached a minimum thickness.
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      02-11-2016, 06:44 AM   #14
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Quote:
Originally Posted by VTECaddict
Quote:
Originally Posted by RL325xi View Post
Robertrichy,

I think I will do the same. I will replace both front and back sensor. and hopefully, it will allow me to reset and turn off the brake warning light.

will report here once I replace them.

Thanks all
Just plug in the new sensor and reset, then go back to the old sensor. People also do this by shorting the two wires together instead of a new sensor.

If you use the new sensor with worn pads, all you're going to do is just crush/break the new sensor when you apply the brakes.
So you're saying just unplug the old sensor, plug in the new one then reset the service indicator. Then plug the old/worn/broken sensor? Won't it automatically trip the service light again?
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      02-11-2016, 07:40 AM   #15
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Quote:
Originally Posted by N54CherryHill View Post
Just push the damn handbrake down
This is why this is confusing... The low pad warning is the same light as the "Brake" light when the hand brake is on except when you pull the hand brake while the car is moving a second symbol, a yellow brake icon comes up in the gage cluster and a alarm chime sounds. That how you know the red "Brake" icon means the brake pads have warn to their minimum thickness.
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Last edited by Efthreeoh; 02-11-2016 at 07:55 AM.
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      02-11-2016, 07:53 AM   #16
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Quote:
Originally Posted by RobertRichy View Post
So you're saying just unplug the old sensor, plug in the new one then reset the service indicator. Then plug the old/worn/broken sensor? Won't it automatically trip the service light again?
OP, it is most likely that your pads are actually worn out and the brake system is telling you so. The CBS keeps track of the wear rate of the pads by the wear on the sensor. The sensor is dual-stage, which means it wears halfway through and records the event in the CBS computer (a loop of wire imbedded in the sensor breaks). The second stage is when the second wire loop in the sensor breaks which triggers the red "Brake" icon. When that happens the CBS menu will show either the front or rear axle at -- miles left on the brake pads. It does that so you know which axle needs new brakes. The sensor is dual-stage so as to provide an actual wear rate of the pads, which allows the CBS to estimate the remaining miles left on the pads. However once the 2nd wire loop breaks and the "Brake" icon comes up, one or both sets of pads are worn out and need replacement.

By trying to reset the CBS you are just confusing the logic built into the software. This is why whenever you replace brake pads on a BMW you replace the sensor and reset the system. The system uses a algorithm of a predetermined wear rate along with the real wear rate as determined by the sensor wear rate (the 1st wire loop breaking) to provide an estimate of the miles remaining on the pads. So if you perturb that sequence and not reset the CBS and the Brake Wear System (by using new wear sensors) you get things fucked up and the system reports erroneous information.
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A manual transmission can be set to "comfort", "sport", and "track" modes simply by the technique and speed at which you shift it; it doesn't need "modes", modes are for manumatics that try to behave like a real 3-pedal manual transmission. If you can money-shift it, it's a manual transmission.
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      02-11-2016, 09:04 AM   #17
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Quote:
Originally Posted by VTECaddict View Post
Just plug in the new sensor and reset, then go back to the old sensor. People also do this by shorting the two wires together instead of a new sensor.

If you use the new sensor with worn pads, all you're going to do is just crush/break the new sensor when you apply the brakes.
best advice thus far. It's plain stupid for people to say put the handbrake down.

Example, you do not need functioning ABS at many state safety inspections, but you cannot pass if you have a red brake light on. That does indicate that the parking brake is on in many vehicles, but it doubles as a system failure warning light as well.
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      02-11-2016, 09:05 AM   #18
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Quote:
Originally Posted by Efthreeoh View Post
OP, it is most likely that your pads are actually worn out and the brake system is telling you so. The CBS keeps track of the wear rate of the pads by the wear on the sensor. The sensor is dual-stage, which means it wears halfway through and records the event in the CBS computer (a loop of wire imbedded in the sensor breaks). The second stage is when the second wire loop in the sensor breaks which triggers the red "Brake" icon. When that happens the CBS menu will show either the front or rear axle at -- miles left on the brake pads. It does that so you know which axle needs new brakes. The sensor is dual-stage so as to provide an actual wear rate of the pads, which allows the CBS to estimate the remaining miles left on the pads. However once the 2nd wire loop breaks and the "Brake" icon comes up, one or both sets of pads are worn out and need replacement.

By trying to reset the CBS you are just confusing the logic built into the software. This is why whenever you replace brake pads on a BMW you replace the sensor and reset the system. The system uses a algorithm of a predetermined wear rate along with the real wear rate as determined by the sensor wear rate (the 1st wire loop breaking) to provide an estimate of the miles remaining on the pads. So if you perturb that sequence and not reset the CBS and the Brake Wear System (by using new wear sensors) you get things fucked up and the system reports erroneous information.
Good explanation. A spare non OEM sensor cost me like $12 at FCP. I just bought in case I ever need it.
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      02-11-2016, 09:15 AM   #19
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In most other cars, the brake light performs two functions:
- Indicates the emergency brake is on
- Indicates you have a loss or imbalance of fluid pressure from front to rear or vice versa

Normally I check the handbrake first as this is the easier check. If the brake is released, check the cables and the e-brake mechanism to see if either of them are stuck and leaving the e-brake on or partially on.

If neither of these, it is possible you have a fluid problem in the master cylinder. The cylinder is divided into two separate hyrdraulic control zones, front and rear. This is for safety so that if pressure is lost in half the system, you still have braking in the other half. There is a switch in the master cylinder that compares the pressure between the two sides of the system. If they are severely imbalanced, the brake warning comes on.

If this is the possible cause, look for leaks. If none are found, bleed both the rears and fronts. See if this causes the light to turn off.
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      02-11-2016, 09:27 AM   #20
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Quote:
Originally Posted by ZhengHai View Post
I just remember that dealerships won't even replace pads until they're reached a minimum thickness.
4.5mm is the point where we can replace them. just under 25% life remaining.

BMW has been coming down on brakes since there was alot of pad replacements happening with 7-9mm remaining because the CBS was going off
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      02-11-2016, 09:30 AM   #21
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Quote:
Originally Posted by robthewrench View Post
In most other cars, the brake light performs two functions:
- Indicates the emergency brake is on
- Indicates you have a loss or imbalance of fluid pressure from front to rear or vice versa

Normally I check the handbrake first as this is the easier check. If the brake is released, check the cables and the e-brake mechanism to see if either of them are stuck and leaving the e-brake on or partially on.

If neither of these, it is possible you have a fluid problem in the master cylinder. The cylinder is divided into two separate hyrdraulic control zones, front and rear. This is for safety so that if pressure is lost in half the system, you still have braking in the other half. There is a switch in the master cylinder that compares the pressure between the two sides of the system. If they are severely imbalanced, the brake warning comes on.

If this is the possible cause, look for leaks. If none are found, bleed both the rears and fronts. See if this causes the light to turn off. If the light is still on, see a pro.
If you have a low brake fluid light it will set a fault and have DSC light comes on.

and he said the parking brake was down, so unless the contact wire shorted or became disconnected its not the parking brake since that purely mechanical and only has one monitor (the single spade connection at the handle looking for contact)
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      02-11-2016, 01:01 PM   #22
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Quote:
Originally Posted by John 070 View Post
best advice thus far. It's plain stupid for people to say put the handbrake down.

Example, you do not need functioning ABS at many state safety inspections, but you cannot pass if you have a red brake light on. That does indicate that the parking brake is on in many vehicles, but it doubles as a system failure warning light as well.
I don't know if you took it serious but it was a joke..
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