Can anyone tell me what this plug is/does? - Mercedes-Benz Forum

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post #1 of 4 (permalink) Old 01-07-2011, 05:52 PM Thread Starter
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Can anyone tell me what this plug is/does?

On January 6th, 2011, my brother and I took his Mercedes 420 SEL into the local JiffyLube for a routine oil change. When we turned it over to the technicians, they couldn't start the car. We discovered that the buggy alarm system (a problem that was supposedly fixed years prior) had somehow tripped and locked the car down in front of the service garage. After explaining this to the techs, the three of them jumped into the driver's seat one-by-one (without asking) trying to find the wire that controlled the alarm so they could disarm it. After they gave up with the alarm, my brother and I ultimately disarmed it by locking all the doors, then unlocking them each in turn (Don’t know why that fixed it, but it’s a home remedy we discovered on the spot) and they went ahead with the oil change. Following the oil change, however, the car couldn't keep running at idle speed, requiring near red-line rpm just to keep the engine running. This was not the alarm system locking the car down; the ignition wouldn't even start the engine were that the case. Clearly, a new problem had arisen after the JiffyLube techs had frenetically pulled whatever wire they "Thought" would disarm the alarm. Of course they called it coincidence, deciding instead to insult the car’s ability to start and mocking our ability to maintain it. After getting the car home (and having it quit three times on the way) and troubleshooting for a day, we discovered this plug (pictured below, center of the image) completely removed from its socket. After plugging it back in, the car sprang to life and ran as well as it did before its stop at JiffyLube. This plug is located in the dashboard, to the left of the steering column and is virtually impossible to dislodge by accident. It appears that while the JiffyLube techs were attempting to disarm the alarm system, someone pulled this plug free, did not tell anyone what he had done, and didn't think to replace the plug once the alarm had been disarmed by other means. I would like to know what this plug does and why the engine will not run properly when it is unplugged so that my brother can know exactly what it was that the techs “thought” was the alarm’s power plug.

The same plug, as it was found after the oil change at JiffyLube:

I apologize for the poor quality of the pictures. It took some creative angles to get it into frame because of where it is positioned. Any insights or ideas as to what this does for the car would be greatly appreciated, thank you.
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post #2 of 4 (permalink) Old 01-07-2011, 06:44 PM
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Originally Posted by Little Mac W126 View Post
On January 6th, 2011, my brother and I took his Mercedes 420 SEL into the local JiffyLube
You are not going to win popularity contest on this forum.
The plug looks like 100 other plugs on the car. Take it to W126 forum, maybe fellow model owner will have better idea.
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post #3 of 4 (permalink) Old 01-07-2011, 07:31 PM
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>>the car sprang to life and ran as well as it did before its stop at JiffyLube.
You should name it the Life Plug and award yourself a beer.
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post #4 of 4 (permalink) Old 01-07-2011, 08:39 PM
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Glad you are running well again and I hope this taught you a lesson. I would not take ANY car to a Jiffy Lube for anything.

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