Lenovo A485/T480 USB stops working when USB2.0 is plugged.

[someonenotyou]

Hi.

I have 2 Lenovo laptops (A485 and T480) with identical USB problem.
When I plug in a USB 3.x device (USB storage), the USB ports are working normal.
But as soon I plug in USB 2.0 device (mouse, USB storage), all the USB ports stop working. Even if I plug in USB 3.x device.

The only way to get USB working again is disconnect battery and reset BIOS.

Has anyone had anything similar?
I have not yet tried another BIOS, but would that be the problem with USB?

Thank you.

[someonenotyou]

I finally received 1.8V conversion board and flashed a different BIOS. Still no changes.

Board - Lenovo A485 NM-B711

I started to test resistance on USB 2.0 D+ and D- pins. Almost all of them had 0,6Mohm resistance, except D- line going to a USB C port, which had only 2ohm resistance.

I desoldered the L74 component, but the 2ohm resistance still remained. And the line goes straight to CPU.
Does that mean the USB 2 controller in CPU is bad?

But the Web Camera, which is using USB 2.0, still works.


Any ideas?

Thank you.

[mon2]

Flux and carefully remove D4058 off the board. Measure the resistance to ground again after this removal - leave this TVS ESD device off the board.

< Assuming this part is onboard >

Update - measure the resistance from the TVS ESD diode to the CPU. Is there a low resistance? This is to confirm that you have truly isolated the connector side from the host side. Aside from the 2 x ESD diodes on the USB connector & L74, the CPU is the host controller so it appears it is damaged (to me).

[someonenotyou]

...

Thank you for reply.

Made the measurements:

D4058 Pin 1 > L74 Pin 1 = 0ohm
L74 Pin 1 > L74 Pin 2 = O.L
L74 Pin 2 > GND = 2ohm

Anyway, I removed the TVS, but still no changes.

All this started to happen after BIOS update (according to my colleague)

[Sephir0th]

It's a partially fried chipset. Happens regularly. Possibly reason could be that something faulty was inserted in on of the slots but no clue unfortunately.

I wouldn't recommend voltage injection here since there is a decent chance that the chipset will blow up.

[someonenotyou]

...

Yeah, voltage injection is out of question. CPU still works, and there are no other components that could be faulty.

[noipi]

flash another bios, not the read one..get it from the site or read from another working unit.

[mcplslg123]

This is not bios issue for sure. You already got the correct advice at post#5