[Sprint Galaxy S 5 Q&A, Help & Troubleshooting] saber0091:
Same problem here too. Search results don't seem to be helping so far.

Shows up fine in Odin3_v3.12.3.exe , run as administrator.

SM-G900P running "G900PVPU2BOD3_G900PSPT2BOD3_SPR", so Android 5.0 OD3, kernel version 3.4.0-4631307.

Phone set to "CDMA Modem" and "RNDIS + DM + Modem" modes, via dialer code "##3424#".

"USB Debugging" mode already turned on (but keeps turning off on every reboot).

SAMSUNG_USB_Driver.exe version 1.5.51.0 installed successfully on Windows 7 x64.

Phone shows in Devmgmt.msc as "SAMSUNG Mobile USB Modem" , driver version 2.11.11.0.

QPST 2.7 Build 4.1.1 installed successfully.

"QPST Configuration" > Ports > "Add New Port" , shows:

"COM1 - Serial (Communications Port)"

"COM3 - USB/QC Data Modem (SAMSUNG Mobile USB Modem, xxxxxxxx)"

"COM4 - USB/Unknown (SAMSUNG Mobile USB Serial Port , xxxxxxxx)"

Placing a checkmark in "Show Serial and USB/QC Diagnostic ports only" hides the second two.

But selecting any/all of those three results in the QPST Ports screen showing "No phone connected" for each.

Tried DEVMGMT.MSC > Right click "SAMSUNG Mobile USB Modem" > Update > Browse > "Let me pick" > "Show compatible hardware" checkmarked , which shows 4 results with same name. Tried each one, no change.

Any ideas?

---- EDIT 20170104 ----

Managed to get much further, after much research and many hours of messing around.

Unless I am mistaken, the option "CDMA Modem" (via dialer code "##3424#" , or "CP" via dialer code "*#0808#") just doesn't want to stick.

But the main problem now is that the communications connection just seems to reset or something after a short time.

My process:

Devmgmt.msc > modems > RIGHT CLICK on "SAMSUNG Mobile USB Modem" > Properties > Modem tab > Com port at top.

QPST Config > Ports > Add New Port > UNCHECKMARK "Show Serial and USB/QC Diagnostic ports only" box > Should be 3 ports, ignore COM1 and the same COM port as listed in DEVMGMT.MSC , use the remaining one.

Example:

COM3 is reported in DEVMGMT.MSC for "SAMSUNG Mobile USB Modem".

In QPST:

"COM1 - Serial (Communications Port)" --(Shows also when box is checkmarked.)

"COM3 - USB/QC Data Modem (SAMSUNG Mobile USB Modem, xxxxxxxx)"

"COM4 - USB/Unknown (SAMSUNG Mobile USB Serial Port , xxxxxxxx)"

So add COM4, (Also, optionally: Right click COM4 in the "Ports" tab of the main QPST window and click "switch modem port to diagnostic mode").

Then "Start Client" menu > "Software Download" option > new popup window happens > "Backup" tab > Input the SPC (MSL) code in the box ("000000" gave error: "SPC given could not unlock the phone", so called Sprint and got the real MSL / SPC code) > "Start" button > then always at 12% comes "Status: Memory Backup Failed" and "Errors: Could not Communicate in Diagnostic Mode".

Close QPST Configuration program.

Open QPST Service Programming (ran as Administrator) program.

New phone connection > select phone > "retry" a bunch of times > "UMTS System" tab > "Read from phone" button > prompted for MSL, so I put in the MSL > wait > "The phone has stopped responding to memory read/write commands".

So the problem appears that the communications connection seems to reset or something after a short time.

Any ideas?