Hi again and thanks for doing that TEST.
By the way, we only need to push on the DEVICE END - as that is what we are testing for - a loose connection there.
AND we should START with the device ON, and then connect to USB cable at the back.
So what I suspect is that the USB connector is "broken" - inside the device. Let me give you a link to a page that has a picture of what I suspect >> Click Here<< When on that page, scroll down a bit until you see the CLOSEUP of the connector - with two red arrows. I suspect you have similar damage - except on the DATA pins - in the center of the connector mount.
So I will let you know that the folks at that site I linked to do repairs of these units - if you can get a quote for the repair and send it to them (they get very busy). Look for the "Request Quote" button on the left column of the site to see if you can get in.
You can also try to have the device repaired by Garmin, using the following link. These repairs would be for a flat fee, as the is well past its standard 1 year warranty, To get a qoute, select your model number from the pull-down list. Then scroll down to see the rest of the steps for sending the device in for repair.
Once you look at the cost of repair, you may also want to consider replacing the device with a newer model. I say this because the prices of these devices has dropped quite a bit in the last year or so, and often it is less expensive to get a newer unit than to have the older model repaired.
As a reference only, I did a search on Amazon for "Nuvi LM" (includes Lifetime Map updates), so you can see the models available and the "street prices" you can expect for the current models.
Nuvi LM Search Results
Sorry for the diagnosis of this issue, but I'm about 98% sure of what is happening, as I have seen this on MANY models of this type.
Please let me know what you find or if you have any more questions.
Thanks, ***** *****