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Thread: Need electrical help or a match

  1. #1
    Join Date
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    Need electrical help or a match

    I bought a 04 Z4 E85 2.5 Auto for my 15 year old daughter to teach her some mechanical stuff. Car has only 62k on it but needs a ton of stuff, has been a great project so far but I need some electrical advice/help. First I'll start out by saying the car sat for awhile, had some mouse poop in it, but it runs and drives great after a few mechanical repairs, water pump, thermostat, evap tank, front suspension & brake parts. However I need it to pass emissions and it can't have any lights on the dash and well its has a few, airbag light, SRS (steering), ABS/Traction control comes on occasionally while driving even after all new brakes and wear sensors, I cleaned the wheel speed sensors but probably should take ohm readings (I thought scanner would pick up).

    The other odd stuff is that when you turn off the key sometimes the car keeps beeping until you unplug the battery, the temp reading on the dash says -40 and stays there and I am in AZ where its 90+, the radio reads disabled but still works, the clock shows ----, and the motor for releasing the convertible top is sporadic (and I have removed and tested the motor & replace gears) and the hydraulic pump was in a bath of mud and I have removed the motor for now with plans to replace later.

    I have downloaded and attempted to install INPA & virtual machine software and it has a problem reading codes, IPNA shows battery and ignition when I turn on the key but says it can't connect to read codes. Emailed back and forth with software guy and he thinks its either a bad cable or computer could be jacked. I also bought Foxwell scanner and it is able to pull some of the codes so maybe it is the cable? Foxwell codes are 5E40 steering angle implausable, 611C EPS Steering torque, 61 EGS Battery Voltage supply terminal 30, 87 KOMBI K bus, CE Outside-temp sensor, BE KOMBI Data-filing difference to central light module, and 20 Airbag warning lamp. The car when I bought it came with a new Interstate battery, I have it charged and it tests at 12.4V. I am going to take the battery tomorrow to have it tested.

    I have read about lots of Z4's with these gremlins and curious if people had any thoughts? Even if I removed steering column to replace angle sensor and torque ribbon and found the airbag problem it still has lots of other electrical issues. Seems like maybe too many problems to be the GM5 module? Is there a K-Bus responsible for spreading power to modules? Or could my computer just be jacked? I have a carfax that shows no damage and I don't see or smell that it's been flooded, it's a CA car. Appreciate any thoughts and or help!
    Last edited by onequik1; 06-01-2022 at 11:22 AM.

  2. #2
    Join Date
    Mar 2021
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    1987 325is, 2006 Z4 3.0i
    So I will start by saying that you could have failed electronics based on the condition you mention the car was in, however a lot of your issues could be related to battery disconnect or sensor disconnect when working on it as well as low voltage (battery not fully charged) as I have experienced some similar issues.

    I got the airbag fault after I had one of the seats out diagnosing something else and turned the key on to accessory tripping the seat sensor code.

    Also got the steering fault after an alignment was done.

    I’ve had several other faults pop up related to the battery voltage dropping below around 11 volts when it wasn’t on a trickle charger or running periodically.

    My advice would be to hook the battery up to a charger to maintain proper voltage (or get a new one if yours is too far gone) and use the Foxwell scanner and reset the codes. Keep the voltage steady and see if the codes come back. If they do, then you can start digging into the actual sensors and faults once you know it’s not just a dumb voltage issue.


    dj Roo
    ‘87 325is, ‘06 Z4

  3. #3
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    I left charger on over night and battery was just over 13 volts, when I hooked up Foxwell scanner it read 12.2 at the ODB port. I did reset a few of the codes however 2 that I can not reset are the airbag light and the steering light. I also am not able to determine other than the generic airbag code "20" even which airbag it is. How did you figure out which one yours was? Or did you just know because you had the seat out? I also installed IPNA and EDIABAS software but needed to order another cable, hoping with that software it will tell me more specifics.

  4. #4
    Join Date
    Oct 2012
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    So agree that likely low voltage battery issues …

    Since you had the battery out (I have ‘04) clean/check the twisted pair connector that is next to the wiring block in the battery well… left of it. The twisted pair connects to the BST on the battery cable. This twisted pair is part of the SRS wiring and the resistance of this wire is monitored.

    It’s possible that while changing battery to disturb the connection.

    If the connector is dirty the resistance increases … and an error code is set. (Seat belt light)

    INPA and INSTAD can actually measure the resistance and tell you if it’s in spec..

    After 8 years of having to clean this connector when it faulted I replaced the connector last summer.

    You have to clear the codes as suggested and then see what comes back.

    Always disconnect battery cables when working on/disconnecting connectors… error codes will be set otherwise.


    Sent from my iPhone using Tapatalk

  5. #5
    Join Date
    Sep 2018
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    Mechanicsburg, PA USA
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    2003 2.5 BMW Z4
    I agree with the other posters that your electrical issues might be caused by your battery. However, another possible cause is a faulty ignition switch, on BMW's, they can cause all kinds of very odd electrical problems, just like a failing battery. The good news is that ignition switch's are easy to change out and aftermarket switch's on ebay are not costly. Please read: https://www.bimmerfest.com/threads/s...switch.358204/ afterwards google BMW faulty Ignition switch for more info.

  6. #6
    Join Date
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    If you are having trouble with INPA not reading anything other than the DME then I suggest taking apart the cable and soldering pins 7 and 8 together. I was having this same issue until I did that, now INPA works perfectly.

    Your issues sound a lot like what I have been dealing with, and I have managed to get them down to just the steering and airbag lights.

    I would suggest getting INPA working, then do a complete erasing of the error codes, restart the car, and see what comes back up. I found a bad yaw sensor that lit up a bunch of lights, and replacing it resolved most of that. The steering and airbag lights could be something else, and I suspect the "disabled" on the radio could be bad wiring at the central module under the rear of the console, behind the parking brake. Water gets in there, corrodes everything, and causes issues with the K-bus, causing the "disabled", and also making windows not work at times.

    To clear airbag errors in INPA you need to do it from the Safety Information Module menu.

    I had these issues and was able to get them tracked down.
    Last edited by clarkitect; 06-02-2022 at 04:09 PM.
    2000 740i Sport | 2004 330xi | 1988 325i Vert | 2003 Z4 2.5 | 1995 Ford F150 | 2018 GTI

  7. #7
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    I had a cable that has a dip switch and confirmed with vendor which position closed pins 7&8, cable worked sporadically so I just ordered a new one.

    Been reading tons and think I have a plan, the airbag I am thinking could be the passenger side mat sensor which sounds painful and or expensive to replace. I found a site that sells a bypass connector for $30, cheap easy solution so I can get it to pass emissions.

    Next I am thinking to replace the ignition switch as others mentioned because it's like when you shut off the car and remove the key sometimes the dash stays on and the car beeps like the key is in it. Both this issue and the airbag mat people have claimed it can cause ABS and other issues. I also read that one failing module can mess up the GM5 bus? Finding and fixing that module can solve other issues.

    If all that doesn't solve my issues I am going to yank the steering column and look at the torque ribbon at the bottom of the column. I'd either attempt to repair it or I found one in a bone yard. If you repair or replace the torque ribbon there is alignment that looks painful and if you replace the column it seems like you have to program some stuff. I do have the ability to program the steering angle but not sure what else.

    I'll keep this thread posted as I go and certainly appreciate peoples responses!

  8. #8
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    "when you turn off the key sometimes the car keeps beeping until you unplug the battery"

    For what its worth, My old 03 2.5i did that as well.It only happened about once a year, and would stop after 5 minutes. No codes...I never figured out why.

  9. #9
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    I finally got DIS software to work with my new cable. In going through Diagnostics there are lots of errors and it can read many modules. I do still need to take my battery in and have it tested, however it still shows as 13V @ battery and over 12 via ODB connection. The two main things I really need fixed to clear dash lights so I can get emissions are the steering light and the airbag light. According to DIS diagnostics it can not communicate with the electronic steering, the SIM(safety information module)/Airbag ECU, or the SM5 module.

    I would note that for the steering it does steer heavy and there appears to be no electronic assist going on. When I went into troubleshooting that module it read there was no power to the unit. I have checked all the fuses on the fuse box so far.
    Last edited by onequik1; 06-03-2022 at 02:36 PM.

  10. #10
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    Have tried IPNA, DIS, and Foxwell scanner software and none of them can communicate with SM5 module or Airbag Module. I have to assume this is the root of some of my issues. Can anyone confirm that any of these methods should be able to read those 2 modules?

  11. #11
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    Think I found my answer on another post.....I am getting the IFH-0009 error from DIS/IPNA when attempting to connect to either module. Guess I will work on finding someone to repair, or buy used ones and recode them.

    Last edited by onequik1; 06-03-2022 at 11:51 PM.

  12. #12
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    Airbag functions are in the safety information module and various other modules in that menu. I would check the module in the back end of the console for water damage. If you had mud in the convertible top motor are I would guess that could have gotten under the carpet. Damage to that module could result, and it’ll drag down the k-bus comminications with other modules. I literally just went through this.







    Repaired the connector, replaced some pins in the module, and a lot of gremlins went away.
    Last edited by clarkitect; 06-04-2022 at 10:07 AM.
    2000 740i Sport | 2004 330xi | 1988 325i Vert | 2003 Z4 2.5 | 1995 Ford F150 | 2018 GTI

  13. #13
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    Wow, sort of good but bad right? I took my battery in and had it tested and it tested good. I then saw your post and can confirm my the hydraulic pump I pulled out for the convertible top was sunk in what I can only describe as mud. So since I planned on removing both the GM5 module and airbag module I wondered what the rest of the car looked like with all the wires under the carpet so I pulled out all the carpet. Unlike yours mine was pretty clean, I can confirm the only thing that appears to have gotten wet was my hydraulic pump convertible top pump, which I currently have removed. I have so many other issues I planned on coming back to the top last. I am thinking about sending my airbag & GM5 module in to have it tested and or cloned with a used one. I have read the steps to reprogramming modules and seems possible but not worth my time to figure out. I think both those modules have to be programmed based on what I have read.

    One other thought is, since I have all this out is to visually inspect the wiring and maybe find some schematics to test a couple wires to these units. My cpu for the convertible top was shockingly completely dry.
    IMG_8655.jpgIMG_8656.jpgIMG_8657.jpg

  14. #14
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    Wow yours looks clean. Mine was in a Vermont field for a number of years and was def not that nice.

    Something must be up with your inpa but I don’t know. I’m lucky to have gotten as far as I have with my pos.
    Last edited by clarkitect; 06-05-2022 at 01:59 AM.
    2000 740i Sport | 2004 330xi | 1988 325i Vert | 2003 Z4 2.5 | 1995 Ford F150 | 2018 GTI

  15. #15
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    Quote Originally Posted by onequik1 View Post
    However I need it to pass emissions and it can't have any lights on the dash and well its has a few, airbag light, SRS (steering), ABS/Traction control comes on occasionally while driving even after all new brakes and wear sensors, I cleaned the wheel speed sensors but probably should take ohm readings (I thought scanner would pick up).
    While you should fix the issues causing those lights for the sake of safety of the driver and other cars on the road, I have never once heard of these error lights preventing the car from passing smog/emissions. They look for check engine lights (which indicate issues with emissions systems), not ABS, brake, or other auxiliary warning lights.

    Going into my TENTH YEAR of providing high quality reproduction BMW fabrics!

    PRICE CUT on ALL FABRICS
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  16. #16
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    I shipped my airbag control unit off to have it tested. If they can read it but my scanners can't then I think I need to start looking hard at the K BUS. From lots of reading the dash cluster ties heavily into the K BUS, and I did have an error on the K BUS 87 K Bus short circuit to negative, working my way thru schematics to figure that out.

  17. #17
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    Got my airbag control unit back and it tested good, so it was not the root cause of my problems. I also got a used steering column and instrument cluster. The steering ribbon inside the column was my steering problem, so replacing the column got me power steering back. I tried the used instrument cluster as All Data has the as being the #2 issue with the Z4's but that also did not cure my issues. The main problems I was having up to this point were air bag light on dash, central lock button didn't work, no interior lights, ac compressor no kicking in, radio showed disabled, dash beeping after key removed. Per DIS scans I was having a K-Bus issue, I found this site https://www.bmwgm5.com/default.htm which was amazing. I was able to find the one wire that was causing a drop in voltage and still need to trace it out, I assume it's the wire going to the airbag module and will trace out. After following this troubleshooting my radio is fixed, the AC is working, no beeping after key is removed, I also figured out my center console lock/hazzrd button was bad and my interior light unit was bad so those were unrelated. Now all I have left is to trace out the one wire I have disconnected and hope that its to the airbag control unit. One addition the website for troubleshooting K-Bus error on the Z4 (or at least 04) is that the black box with the wiring is not on the back of the fuse box, it is mounted to the firewall and to get it off it has two tabs and you need to push it straight up to get it off.

  18. #18
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    Read my post #4….. if you have an airbag light and you are getting a low voltage/high resistance fault…. Look at that connector in the battery well to the left of the wiring block on the drivers side of the battery. That particular connection can give a low voltage/high resistance fault. After 8 years of cleaning that connector for the issue I replaced it with a new connector that had the same gauge wire. Resistance is back in spec now…

    You can delve further into the error code to test the actual resistance of the circuit.

    Download INSTAD which is the new version of INPA … it’s easier to use diagnostically than INPA.

    Reconnect that wire… clean that connector (2wires), clear the airbag light and see what happens. If you get an airbag light again… follow the fault code down the rabbit hole of possible causes….


    Sent from my iPhone using Tapatalk

  19. #19
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    Can you tell me which connector by the battery? IMG_8748.jpg

  20. #20
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    Very very left bottom of picture.. on the block on the battery wall… there is a connector to the left side as you look at it… it clips on … 2 wire connector. The wires from it go to the end of the BST on the positive cable that you see at the top left of the picture. It’s part of the SRS circuit.

    On your picture the wires from the connector to the BST appears to be encased in a black plastic “sheath”….

    That connector can show up as a high resistance fault. The range is 1.2-3.4 ohms.

    Use electrical cleaner and reconnect.

    Disconnecting the SRS connector sets a fault/airbag light and memory code which needs to be reset.


    Sent from my iPhone using Tapatalk

  21. #21
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    Before I check the battery get this, like I mentioned before I sent in my airbag module and they said it tested good. The one wire I disconnected from the spade block of wires behind the fuse panel I traced out with a tone tester and it goes to my airbag module. I ran a new wire, checked resistance and wire is good. When I plug it into the airbag module my issues come back instantly. Disconnect airbag module and problem goes away. So this has to mean there is some sort of internal issue with the airbag module not a bad wire. Going to get a used module and hopefully that puts all this to rest. Anyone know if I will have to program a used module and any tips for that?

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