Dell XPS 13 9370 unknown USB devices in device manager

[Stachujones]

Hello, i bought a faulty Dell xps 13 9370 after installing windows in device manager i Can see 2 unknown devices, one is thingerprint reader because it dissapears after i unplug it and second one is i believe bluetooth because it also doesnt work and in bios there is no bt also.

Device manager says "unknown device, failed to request device descriptor"
Can somebody point me in right direction what to check?
I updated bios to the newest version and thunderbolt controller firmware still no luck

[mon2]

To save time, always share details of the logic board markings so we can track down (if one exists) the schematics.

See attached. Believe you have the 'LA-E67' motherboard?

The fingerprint reader is interfaced through a USB 2.0 port which is protected by local TVS ESD devices. It is very possible that a transient has taken out these TVS diodes and is now causing communication faults.

Remove all power. Meter in diode mode. Red meter probe, yes red to ground. Black meter probe to the point to test. Test each of the USB 2.0 lines used by this fingerprint scanner so test D+ and then D- lines.

Post each measurement which are in volts. If the voltage measurement is too low or close to zero then the TVS diode has triggered and must be removed and/or replaced. Respectively, a shorted TVS ESD diode will raise the observed errors.

[Stachujones]

In diode mode it has 0.495v

If i identified correctly it should be this component?

[mon2]

Red to ground (not the point to test) when using DIODE mode. Repeat testing.

[mon2]

See attached. Post a pic of this region. It is possible that the vendor has not even stuffed this part (to save the pennies to build this board) in which case, the port was never protected against ESD transients. It is a common trick used by the cheap manufacturers.

[Stachujones]

Yeah i done that, Red was on ground while i messured, on this photo Red was just to point at component 😉

[Stachujones]

Here's the photo

[Stachujones]

See attached. Post a pic of this region. It is possible that the vendor has not even stuffed this part (to save the pennies to build this board) in which case, the port was never protected against ESD transients. It is a common trick used by the cheap manufacturers.

Made a better one

[mon2]

Well noted. The diode mode readings are the same as posted for each of the 2 pins on D20 mated with D+ and D-? If yes, the USB lines are not shorted.

[Stachujones]

Well noted. The diode mode readings are the same as posted for each of the 2 pins on D20 mated with D+ and D-? If yes, the USB lines are not shorted.

Yes there are the same, is there any things to check? Is bluetooth related to this?

[Stachujones]

I founded something strange all of the legs of this component are shorted to ground (dead short 0,0ohm)

[mon2]

Flux and carefully remove D20. Protect the nearby plastic parts like the fingerprint cable and connector - otherwise it will melt and warp. Use aluminum foil or similar to protect the plastic part(s) from the hot air nozzle. Point the hot air nozzle in such an angle to avoid melting the delicate parts.

If D20 is truly showing the low diode mode readings, then most likely this D20 is shorted and causing the fingerprint sensor from working.

[Stachujones]

Flux and carefully remove D20. Protect the nearby plastic parts like the fingerprint cable and connector - otherwise it will melt and warp. Use aluminum foil or similar to protect the plastic part(s) from the hot air nozzle. Point the hot air nozzle in such an angle to avoid melting the delicate parts.

If D20 is truly showing the low diode mode readings, then most likely this D20 is shorted and causing the fingerprint sensor from working.

i founded that with thingerprint reader unplugged there is no short on d20 so maybe just the thingerprint reader is bad, But still there is issue with bluetooth bios says "bluetooth none" i read on internet that bluetooth is in the same chip as wifi but wifi is working fine so what i should check?