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Thread: Brake Fail

  1. #1
    Join Date
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    BMW Z4

    Question Brake Fail

    The brake fail light on my Z4 has activated yet the brakes work OK. Rotors and pads were changed 12 months ago and brake fluid was changed recently. Any ideas as to a likely cause would be appreciated. I am thinking of buying an OBD tool but have no idea where to plug it it on the Z4. Can anyone out there enlighten me?

  2. #2
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    Maybe a calipher has seized? Happened to me recently...

  3. #3
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    2004 BMW Z4 3.0i
    I do not think a standard OBD-2 code reader will help with a brake related problem. The standard OBD-2 codes are only things that are emissions related. (They don't care if your brakes aren't working -- as long as you are not polluting!) You'd have to get something more specialized for reading BMW-specific diagnostic codes such as brakes. Regardless, the OBD-2 port is likely located near one of your knees when you are sitting in the driver's seat. For me (USA 2004 Z4), it is near my left knee. For you (Australia), I suspect it would be near your right knee. On my car, there is a small plastic cover that you need to remove to access the port. I'm pretty sure that the rules (law) says that the port has to be reasonably accessible when you are sitting in the driver's seat.

    Also, if you want to get OBD-2 diagnostic codes read without buying a OBD-2 code reader, you might be able to have an auto parts store do that for you at no charge. That's how it works here in the USA anyway. (I bought a code reader anyway, just for the convenience.)

    One possibility for the cause of the problem might be a wheel speed sensor. These sensors are used by the anti-lock braking system. If a sensor were bad (or maybe just dirty?) it would cause a warning light to come on and the ABS would no longer work properly.

    What does the warning light look like? And what year is your Z4?
    Last edited by sgd98; 01-15-2017 at 07:04 PM.

  4. #4
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    Did you replace the wear sensor last time?

  5. #5
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    Jan 2017
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    BMW Z4

    Z4 lights

    Quote Originally Posted by sgd98 View Post
    I do not think a standard OBD-2 code reader will help with a brake related problem. The standard OBD-2 codes are only things that are emissions related. (They don't care if your brakes aren't working -- as long as you are not polluting!) You'd have to get something more specialized for reading BMW-specific diagnostic codes such as brakes. Regardless, the OBD-2 port is likely located near one of your knees when you are sitting in the driver's seat. For me (USA 2004 Z4), it is near my left knee. For you (Australia), I suspect it would be near your right knee. On my car, there is a small plastic cover that you need to remove to access the port. I'm pretty sure that the rules (law) says that the port has to be reasonably accessible when you are sitting in the driver's seat.

    Also, if you want to get OBD-2 diagnostic codes read without buying a OBD-2 code reader, you might be able to have an auto parts store do that for you at no charge. That's how it works here in the USA anyway. (I bought a code reader anyway, just for the convenience.)

    One possibility for the cause of the problem might be a wheel speed sensor. These sensors are used by the anti-lock braking system. If a sensor were bad (or maybe just dirty?) it would cause a warning light to come on and the ABS would no longer work properly.

    What does the warning light look like? And what year is your Z4?


    The car is 1 2005 model E85 ragtop. It is hard to describe the brake warning light. Basically it is the same as the light warning that the hand brake has been left on but instead of being red it is in yellow. Usually it is accompanied by another yellow warning triangle.

    The brake pads were changed a few months ago and yes I fitted new sensor wires. Because of the time since the fitting I can only deduce that I fitted them OK.

    The mechanic just advised that the Code 20 alarm appears to come form the RCM - Light Control Module, which I believe is in the boot near the battery. It is is stuffed they have to be purchased from the UK apparently then programmed by BMW here in Western Australia. I could check the wheel speed sensors for dirt if I knew what they were and where they reside. What and where am I looking?

  6. #6
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    Quote Originally Posted by puggsley2 View Post
    The car is 1 2005 model E85 ragtop. It is hard to describe the brake warning light. Basically it is the same as the light warning that the hand brake has been left on but instead of being red it is in yellow. Usually it is accompanied by another yellow warning triangle.

    The brake pads were changed a few months ago and yes I fitted new sensor wires. Because of the time since the fitting I can only deduce that I fitted them OK.

    The mechanic just advised that the Code 20 alarm appears to come form the RCM - Light Control Module, which I believe is in the boot near the battery. It is is stuffed they have to be purchased from the UK apparently then programmed by BMW here in Western Australia. I could check the wheel speed sensors for dirt if I knew what they were and where they reside. What and where am I looking?


    But wait there is more.....
    Many of the problems appear to have been the result is water in the boot which corroded some wiring connectors. The highly paid technician cleaned the contacts and MOST problems seem to have been resolved. At least I hope so. The main remaining issue is in the Light Control Module and has the code 20 LCM. The diagnostic computer keeps finding the error code but is unable to reset or cure it. Any suggestions?

    By the way tests of the battery confirm it is fine and not the source of any issues.

  7. #7
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    Quote Originally Posted by puggsley2 View Post
    The brake fail light on my Z4 has activated yet the brakes work OK. Rotors and pads were changed 12 months ago and brake fluid was changed recently. Any ideas as to a likely cause would be appreciated. I am thinking of buying an OBD tool but have no idea where to plug it it on the Z4. Can anyone out there enlighten me?
    I had a similar problem with my Z4 and after the Bosch people had it sitting on their tester for a couple of days the fault was diagnosed to a computer fault and nothing to do with the brakes.

  8. #8
    Join Date
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    BMW Z4

    Question Beemer alarm

    Quote Originally Posted by puggsley2 View Post
    I had a similar problem with my Z4 and after the Bosch people had it sitting on their tester for a couple of days the fault was diagnosed to a computer fault and nothing to do with the brakes.
    The brake fault alarm recently re-surfaced on my E85 Z4. The shop in my home town of Perth, Western Australia, has diagnosed the problem to one of two switches in the brake circuits. There are no switches available in Perth from BMW and even if there were they cost an arm and a leg here - about A$800 plus fitting. Australia is renown for spares being very expensive due to the main dealerships stitching up import allowances. Can anyone in the real world point me to where the switches may be available at "reasonable" prices? Bosch parts may be OK.

  9. #9
    Join Date
    Feb 2013
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    FL
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    2007 BMW Z4 E85 3.0 SI
    Not sure which switch you are referring to since you don’t include any part numbers. If you are referring to the brake pedal switches you will need to select the correct one from the following diagram, obtain the part number and google the number to find prices from different online suppliers

    https://www.realoem.com/bmw/enUS/sho...diagId=35_0186

    if this is not the correct diagram then you will have to find the correct diagram and part number of what you are looking for and google for prices.

    I assume you have google and internet since you can chat on this forum. Google is your ‘real world’. Search for anything you need!
    Last edited by tekoo; 11-08-2018 at 05:09 AM.

  10. #10
    Join Date
    Jan 2017
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    Perth; Western Australia
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    BMW Z4

    Beemer alarm

    BMW could sell me new switches for a small fortune but Mr Google sold me two for less than half the price. They have now been installed by the specialist shop and all is well again. Thanks to all for your help and comments.

  11. #11
    Join Date
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    2001 525it
    Did you clean out the drains in the boot storage area

  12. #12
    Join Date
    May 2017
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    Georgia
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    2003 Z4 2.5
    I get the yellow brake light and triangle from time to time. I have cleaned all the wheel speed sensors on my 03 Z4. The lights stayed off for some time, bUT occasionally come back on but disappear with an on/off cycle with the ignition. I plugged in a Creator 310 for BMW code reader and SE20, SE24 came up. I believe these are the brake pressure sensors. Problem is, there are 2 and I need to figure out which one or even both. You can pay as much as 90 or 150 dollars for the sensors. I have seen Chinese knock offs for as little as 15. I would be skeptical of using the cheap ones.

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