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Thread: Strange electrical bug or bad module?

  1. #1
    Join Date
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    Strange electrical bug or bad module?

    Hello all, I'm still pretty new to this forum, and I've tried searching here for this issue but I have had no luck. Maybe someone here has had this happen and can provide some insight?

    Today, I went to unlock my car using the key fob. The doors unlocked fine. I've been driving the car almost every other day, now that it's back on the road after a long down time for repairs (about 3yrs). I heard the rear doors unlock and thought I had unlocked the liftgate in doing so, but when i went to open it, it wouldn't move. Pressing the microswitch button only made the lift gate move slightly in and out, but not allow it to be opened. I pressed the trunk button twice on the key fob, as well as pressing the trunk button by the hood release, but it still did not open.

    Then out of nowhere, I tried locking the doors again using the key fob but nothing happened! It seems the key fob is now completely dead. I can only lock and unlock the doors, lower the windows and open the sunroof by using the key in the driver side door. I'm assuming I'll have to do the battery replacement on the key fob. I can still start and drive the car just fine however, which leads me to believe that the key does have juice left in it but either the body control module for it is not getting the signal, or the signal is not being relayed properly from the control module to the switches.

    The big problem is that now after this event, I cannot open the rear lift gate or the glass using the microswitches on the doors or by using the button up front. The only way I can open the lift gate is by manually operating the emergency open level which I've put a ziptie on ease of operation now.

    When I try to open the rear lift gate using the microswitch on the hatch, I can see it cycle in a circle inside the latch. It goes around in a circle while simultaneously moving the lift gate in and out, but it the latch does not disengage so I can open it. The same goes for the glass, except there is no sound or movement when I press the release button on the wiper arm. To open the glass, I must operate the solenoid manually just as I have to for the lift gate.

    Is this indicative of a module going bad? At this same exact time, I seem to also be having issues with my DSP amplifier as well. The timing is uncanny. I've heard of bad ignition switches causing strange electronic failures to pop up, but I'm not sure this is the case here. It seems like there is something that is not communicating properly, which is causing my key fob to suddenly not work.

    I'm looking at my Bentley manual, and it looks like it could just be a faulty relay. The wiring diagram shows "REAR LATCH K70 ACTUATOR RELAY" inline with all of the options I've detailed above being dependent on the operation of said relay.

    Does anyone have any experience with this? I'm going to look at the K70 relay in the trunk, maybe open up the relay to see if it's stuck, then dig into the GMIII module behind the glovebox tomorrow, but outside of visually checking for corrosion or visible damage, I'm a little out of my league until I can get a diagnostic tool that will read the GMIII module itself.

    Did I activate some kind of valet feature on the key fob? Did I somehow disable my key fob? I've already tried disconnecting the battery for a few hours to see if that would clear or reset things, but that was unsuccessful. If anyone has come across this problem before and can offer some insight, I'd greatly appreciate it. Thanks.

  2. #2
    Join Date
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    Battery voltage is......?

    Running voltage is ....?

    These things get stupid when the voltage gets below 12V
    Current Garage Highlights
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  3. #3
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    Quote Originally Posted by StephenVA View Post
    Battery voltage is......?

    Running voltage is ....?

    These things get stupid when the voltage gets below 12V


    Battery Voltage Resting: averages around 12.20-12.50v (this is a new battery purchased roughly 2mo ago)

    Running Voltage: 14v with no accessories running. 13.8-13.9 with headlights, radio, and a/c with fan on medium.

  4. #4
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    A good fully charged battery should be at 12.6v minimum. Go get that new battery load tested and see how it does, it might have a bad cell that’s just not up to snuff.
    Set the controls for the heart of the sun

  5. #5
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    I disconnected and took the battery over to O'Reilly's today to get it tested. Had them test it with the hand held and the bigger machine. The report on the battery is that it was good. No bad cells, and it was holding more voltage than when I took it out.

    I think I measured it at 12.25v again before disconnecting, then at the store they said it was holding 12.4v but still reported as good.

    I reinstalled the battery and took the car for a drive because I needed gas. Came back after running the radio, windows and A/C. The meter was reading around 13.3v while the car was running.

    It's great having all these electrical nannies, but it really makes me appreciate the simplicity of my e30 more and more

  6. #6
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    I'm going to do a parasitic draw test on it over the weekend and report back.

  7. #7
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    You can start the car - that is due to the chip in the key case still synched to the ews - when you open up the case to swap the battery - don’t lose that chip. If your battery is still good, resynch the key - instructions are out there.

    In order for the latch components to work, the wires that run along the hinges need to be healthy. After 20 years, they take a beating. Also the hinge pins rust thru. If you have a lifelong Texas car, it could be ok, but the wires could be broken. The covers are delicate, and hard to come by, so be careful taking them off.

    I don’t think it is your main battery.

  8. #8
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    Quote Originally Posted by CPHES View Post
    You can start the car - that is due to the chip in the key case still synched to the ews - when you open up the case to swap the battery - don’t lose that chip. If your battery is still good, resynch the key - instructions are out there.

    In order for the latch components to work, the wires that run along the hinges need to be healthy. After 20 years, they take a beating. Also the hinge pins rust thru. If you have a lifelong Texas car, it could be ok, but the wires could be broken. The covers are delicate, and hard to come by, so be careful taking them off.

    I don’t think it is your main battery.

    I had the same thought of checking the wires, as I just replaced the struts. I made sure to be careful with the wires, but I did notice something odd about the loom when I was in there last. It worked still, so I didn't bother with it.

    The question is, why would the key fob not unlock the car if the wires are bad on the liftgate? It seems like when I go to open the liftgate, the microswitch functions, and I see the latch cycle, but the mechanism to undo the latch doesn't engage. I've only confirmed this visually. The release part that has the wire harness connected to it that also allows you to "emergency open" the liftgate is a new aftermarket unit (purchased by the PO).

    Also, while installing a new fender liner today, I wanted to diagnose why my windshield washers were not squirting. While I was in there, I took off the connector for the windshield pump and put my digital multimeter leads on the pins. I wanted to see if I was getting voltage to the pump when I activated it. It turns out, that I had a steady 8.8V hitting the pump!

    So, without having a chance to do the parasitic draw test on the car over the weekend like I had planned, I may have found why my battery is slowly dying after every night. I just need to track down why it's getting constant voltage when the key is not in the car and the car has gone to sleep. I checked the little light on the gearshift panel. It was out, so I'm assuming the car was asleep. I didn't even have my keys anywhere near the car. Oddly, the pump wasn't warm to the touch.

    What gives? Is there another body control module at work here for the washer pumps?

  9. #9
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    Have you checked the terminal box underneath the passenger floor carpet? Right in front of the passenger seat. You might have had water intrusion at some point, and now the terminals are corroded. You might have multiple issues going on and your mind is racked on to thinking it is due to the tailgate issue.
    Set the controls for the heart of the sun

  10. #10
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    Yeah, I've had a little water intrusion, but only in the rear.

    I'll pull the seat and the carpet and report back.

  11. #11
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    Ok, I've been unable to tear apart the car right now, but while I was prepping an old laptop for INPA using Mikes BMW Tools installer, I went out to the car to connect it with my K+D-CAN cable, and got some errors.

    I came in to research, and it led me to this post here on this forum about the IKE having been replaced. It's the last entry by JPO805. It's mentioned that he didn't have a red dot on his cluster for the mileage. I went back outside and looked at mine to find that I have the red dot next to my mileage. This might be why my MID is not displaying the BC functions currently?

    Is it possible that a PO replaced the cluster a while back and never had it recoded? Or recoded correctly? I've also noticed why people were passing me in frustration a bunch lately, my speedometer is reading 7mph faster than my true speed. This was verified by radar, and by GPS. Both GPS and radar listed the same exact speed. I have stock wheels and tires so I know it's not that making the speedo read faulty.

    Tonight I'm going to connect my laptop with the cable and my 20-pin adapter and see if I can access the module and pull some info off it. I've never used INPA before so this will be a learning experience for sure.

  12. #12
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    The red dot is a tell tale sign for inspectors that means the mileage is not correct between the GM, the odometer, and the LCM. The LCM is where the mileage is stored, so maybe somebody swapped out the LCM, and drove the car without coding it, or same thing with the cluster. If your car has the 20 pin Pacman barrel in the engine bay, you need to go through that.
    Set the controls for the heart of the sun

  13. #13
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    Finally had a chance to pull up the carpet and take a look at the junction boxes underneath to see if there was any bad rust or corrosion. This is what I found:
    IMG_20221019_164035.jpgIMG_20221019_163929.jpgIMG_20221019_164327.jpg

  14. #14
    JimLev's Avatar
    JimLev is offline Artifically Aspirated Moderator
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    That could explain a lot of your problems.You can clean up the corrosion with some scotch brite. The crimps on the ring lugs may be a goner.

  15. #15
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    Also de-oxit / contact cleaner. Is that connection found loose?

  16. #16
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    Looking at where the metal was actually contacting the other metal, it looked clean. Is the corrosion see here adding a lot of resistance which is causing the problems?

    I think I'm going to try the deoxit D5 spray first after loosening the connections so I can reach all the surfaces. It looks like a major pain to have to use manual abrasion on all of these contacts considering the carpet is very difficult to pull up without first removing the center console.

  17. #17
    JimLev's Avatar
    JimLev is offline Artifically Aspirated Moderator
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    That looks pretty corroded to me, I’d clean it and then use deox like CPHES suggested.
    Don’t forget to check all of the brown wires connected to the ground shoe.
    IMG_20221019_164327.jpg
    Last edited by JimLev; 10-23-2022 at 10:11 PM.

  18. #18
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    I finally got some free time this weekend and completely disassembled, cleaned, deoxit'd, and reassembled the junction box. I thought that maybe this would help fix my remote door locks working again, but even changing out the battery didn't help that. I tested the old battery inside the key fob and it had 3 volts. So there is something up with the body control module then? Which module do I need to look for? Also, how would I test to see if what I did really had any kind of positive affect? I have installed inpa on my laptop, and I'm still very new to it. I haven't yet messed around with NCS Dummy.

  19. #19
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    That terminal block has been flooded in the past. At least the strands of the copper wire look pretty clean. It will be worthwhile to clean up that oxidation, and find the source of the water intrusion.
    -Donny

  20. #20
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    I've cleaned all the rust and corrosion off, and sprayed with Deoxit D5. Everything was nice and clean when I put it back together. The leak was coming from the passenger door vapor barrier seal having failed, as well as water coming down my A pillar.

    While in INPA trying to look at the rear tailgate control, I had many errors keep popping up. It was like the module has gone bad. Same with the module for the remote system. Where are these modules located, and how do I know which one is which?

    I'm getting thoroughly frustrated trying to learn NCS dummy and INPA. There are over 100 modules in the drop down for NCS Dummy, and LCM has about 20 or so different versions. How do I go about diagnosing a failed module using INPA or NCS dummy?

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