I’ve been dealing with this bizarre issue on my Garmin Oregon 450 GPS, and I need help diagnosing and fixing them. For some reason, I can’t catch a break with these undocumented unsolved mysteries. Here’s the situation:
(Original)Stuck in USB Mode:
When I turned on the GPS, it shows the USB icon as if it’s plugged into a computer for file transfer, even though it isn’t. If I plug in a USB, it works for file transfer. The issue disappears when I cover the pins from the back case (with the USB port) to the main board with electrical tape. When I do this, the device works perfectly fine, but I need a more permanent solution without relying on tape(outside, if I want to load maps I will need to disassemble my gps). This issue was sort of fixed by resoldering the CMOS battery(which garmin says is not needed - 
)
Power Button Problem:
After I desoldered and potentially re-soldered the CMOS battery, the GPS starts when I press the power button, but it doesn’t boot fully. It powers on but does not complete the boot process. The thing with the CMOS battery is, I don’t know if CMOS is the right term. The battery’s voltage is lower than a standard cmos bat, at a shocking 0.24V. This causes me to think it’s either completely cooked or it’s a specialized battery. Either way, garmin’s user manual(link) says it is not needed. See page 36, saying “Data Storage Life: Indefinite; no memory battery required”
Steps I’ve Taken:
I’ve desoldered and attempted to re-solder the CMOS battery (model 10N4). I’ve tried electrical tape on the USB pins, which temporarily solves the ghost USB issue completely even if I press the power button. I’ve put a little bit of isopropyl alcohol down the USB port(device was off, port was disconnected), it’s still drying as I type. I have NOT disassembled any further than the secondary back plate with the battery slots. If someone thinks that will help, I will try to.
Can anyone contribute to this discussion? I have found radio silence online. Thank you very much.
Photos:
The main board of the GPS, with the pins covered up. Back view
The back plate - note the corrosion
The USB pins uncovered.
An overexposed mess showing my shoddy soldering job of the button cell.
Thank you for reading this, and for any ideas you may have.
I don’t think that they’re saying that the button cell is some sort of undying thing, but rather that your GPS traces and such are being written to nonvolatile memory.
I assume that you already went looking for a replacement cell and couldn’t find one, else you’d have replaced it rather than resoldered the existing one.
Assuming that the button cell is actually the problem and that it’s rechargeable, it occurs to me that you might try pulling the cell off again and checking the recharging voltage across the connectors to try to get an idea of what type of cell it is, try getting a new cell with similar characteristics. Might kill the unit doing so if you get the replacement cell voltage wrong, but if it’s not usable now and you’re confident that the cell is the issue…shrugs
To be honest, if I had the unit, I would probably pitch it rather than invest time in fixing it. It looks like this is a fifteen-year-old unit, and my smartphone is probably a more-capable GPS unit running free software. The value of the time I’d spend on fixing it probably exceeds the value of the unit. There’s a reason that consumer electronics repair isn’t much of a business. If you’re viewing the repair as a hobby or something, though, fair enough.