Mutiple function failures
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Mutiple function failures
Sometimes I get multiple functional failures including - the left turn signal blinks very fast, mirrors don't fold or unfold and can't be adjusted, there is a warning that the battery is low in the key fob, the light at the bottom of the door doesn't light, appears the instrument panel flickers. I noticed when I open the door and shut it again everything starts working as normal but sometimes it takes multiple tries opening and closing the door and sometimes only when done very forcefully.
To me it sounds like the wire harness that connects to the door may be faulty in some way and opening and closing the door jiggles the wire and sometimes just enough to make a connection for everything to work again. Maybe it's the door activation switch - is there a switch somewhere that tells the car when the door is open or closed? Maybe it's faulty but I have no idea where this switch is or how it works?
Anyone come across similar symtoms?
To me it sounds like the wire harness that connects to the door may be faulty in some way and opening and closing the door jiggles the wire and sometimes just enough to make a connection for everything to work again. Maybe it's the door activation switch - is there a switch somewhere that tells the car when the door is open or closed? Maybe it's faulty but I have no idea where this switch is or how it works?
Anyone come across similar symtoms?
Last edited by jbauercda; Feb 4, 2025 at 02:25 PM.
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2011 GLK 350 4Matic
With most of the failures not occurring in systems that are really related to the door, my guess is that it's not the door being open or closed, but the physical shock of closing it that's causing a flaky connection to be restored (temporarily). This is the kind of problem that can be a real bear to trace down - it's really going to be easier to fix if it will fail long enough for you to do some serious troubleshooting. Perhaps someone with a FSM at their disposal could look up any module / connector / cable that would be related to all the symptoms / systems you're seeing issues with...
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With most of the failures not occurring in systems that are really related to the door, my guess is that it's not the door being open or closed, but the physical shock of closing it that's causing a flaky connection to be restored (temporarily). This is the kind of problem that can be a real bear to trace down - it's really going to be easier to fix if it will fail long enough for you to do some serious troubleshooting. Perhaps someone with a FSM at their disposal could look up any module / connector / cable that would be related to all the symptoms / systems you're seeing issues with...
I will say that sometimes it doesn't take a big physical shock (ie. slamming the door) to "fix" things temporarily.
Appreciate the help and guidance.
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2011 GLK 350 4Matic
Door switches (the kind that have a little metal post that stick out and get pushed in by the door jamb when the door closes - are a thing of the distant past. I believe that MB probably just uses the status of the door latch to tell the computer when to turn on the dome light(s). Door latch open, lights on... door latch closed, lights off...
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Thanks for that. As I understand things then could be one one two problems:
1) Door wiring harness. If opening and closing the door can temporarily fix the problem then you would think that moving the harness manually would do the same thing if this is the problem?
2) Door switch/sensor If the door latch has a sensor that tells the computer when the door is open or closed. Is this a mechanical sensor associated with the door latch or built into the door latch? Again, opening and closing the door - sometimes quite forcefully resolves the issue could it be the sensor - what would the force of closing the door have to do with the sensor failing or not? Any idea how to test this theory?
1) Door wiring harness. If opening and closing the door can temporarily fix the problem then you would think that moving the harness manually would do the same thing if this is the problem?
2) Door switch/sensor If the door latch has a sensor that tells the computer when the door is open or closed. Is this a mechanical sensor associated with the door latch or built into the door latch? Again, opening and closing the door - sometimes quite forcefully resolves the issue could it be the sensor - what would the force of closing the door have to do with the sensor failing or not? Any idea how to test this theory?
