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Window issues? Try swapping your MPX door computers...

GS - 2nd Gen (1998-2005) Discussion about the second generation GS300, GS400 and GS430 (1998 - 2005)

Window issues? Try swapping your MPX door computers...

Old 11-25-12, 02:34 PM
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Default Window issues? Try swapping your MPX door computers...

Hi all,

I'm Jupiter, I just signed up on here. The drivers window on my 2002 GS300 will go down but not up...or at least it's really screwy when it does go up, takes a ton of fiddling. After a lot of research, I found a solution. There are a couple posts about it on here, but very little details, so I thought I'd write up this easy MPX test.

If you have a similar problem (drivers window wont roll up consistently, but sometimes will) here's an easy, zero-cost way to check if it's the MPX computer that's your problem. All you need is a phillips head screwdriver (OK maybe two, a big and a small head) and a pair of needle nose pliers.

Note: This works slightly differently if you have the same problem on a different window (ie not the drivers window) - check the notes at the bottom for details.

1) Look up any DIY that explains how to remove the door panel. It's just a matter of a few screws.

2) Pop off the door panels on the drivers door and the front passenger door.

3) The MPX boxes are right there - the drivers side one has a sticker that says "E D", the passenger one says "E P".

4) Disconnect both MPX boxes from their wiring. No need to unscrew the drivers side mount, leave the drivers side MPX bolted on.

5) Unscrew the whole passenger side MPX from the mount. You may have to fiddle a little bit to get the wire connectors off, but it should be easy with a pair of needle nose pliers.

6) Take the passenger side MPX over to the drivers door, and plug in the wires just as they were (no need to unbolt the original MPX from this side).

7) Turn on the car and try out your drivers side window (you wont be able to control other windows or use the automatic function). If your drivers window rolls up and down flawlessly, then you know you need a new MPX for the drivers door ($80 on ebay, make sure it says "E D").

Better than trying to test the window motor and the window regulator, huh?


-The rear doors have a different type of MPX. You can perform the same test by swapping the right rear and the left rear, but you can't swap the rears with the fronts.

-I never tried using the drivers door MPX to test the front passenger window, but I would imagine that's an option too (if your front passenger window is misbehaving).

Jupiter Henry
2002 GS300 Sportdesign
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Old 05-13-17, 10:54 PM
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thank you so much. this just solved my issue
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Old 05-15-17, 09:04 AM
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Originally Posted by creton300 View Post
thank you so much. this just solved my issue
search win.....
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Old 05-16-17, 07:48 AM
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Added to DIY / FAQ thread.
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