English Community

ThinkPad NotebooksThinkPad: T400 / T500 and newer T series Laptops
All Forum Topics
Options

2 Posts

07-04-2015

London

3 Signins

34 Page Views

  • Posts: 2
  • Registered: ‎07-04-2015
  • Location: London
  • Views: 34
  • Message 1 of 3

T420s fingerprint reader connected but not detected when powered on

2015-07-04, 20:45 PM

Hello,

 

I have a T420s running Windows 8.1 (although this has also been tested with Windows 7 and Ubuntu 15.04).

 

When I first got the laptop two weeks ago the fingerprint reader was working correctly in the factory Windows 7 image. I formatted and installed Windows 8.1 Pro. The fingerprint reader worked perfectly.

 

Three days later the fingerprint reader suddenly "vanished". Windows could not see it in device manager. The Lenovo fingerprint reader software could not see it and, most interestingly, the BIOS could not see it. I confirmed this by booting into the BIOS, selecting fingerprint options and trying to reset fingerprint data for which it says no device detected.

 

However when I power the machine off the green fingerprint LED lights up! Not only that but it also powers on if I swipe! However if I then boot into Windows or the BIOS it will say no fingerprint reader has been detected.

 

I am at a total loss as to how to resolve this. Before I did the Windows 8.1 install I updated the BIOS to 1.39, the latest version available. However the fingerprint reader was working just fine for three days before it suddenly stopped.

 

I have already posted about this on the thinkpads.com forum here http://forum.thinkpads.com/viewtopic.php?f=45&t=118218

 

You can see from that thread I have been trying many things to get it to work but nothing has worked so far. I really am at a total loss. I can't think what could be wrong, it doesn't seem to be hardware failure because it does still work when the machine is powered off.

 

I have tried taking the palm rest off and reseating the cable (it shares the same ribbon as the trackpad by the looks of it and the trackpad works just fine). I have tried different BIOS levels. I have tried different operating systems. I have tried leaving the machine powered off with no battery or mains power to see if power drain will "reset" it but nothing works!

 

Now one hint I found online, but stupidly did not bookmark so cannot find it to check again, was that some people have found the fingerprint read dies when used as a power on button replacement. That is they swipe to power on rather than press the power button. Does anyone know anything more about this?

 

Many, many thanks in advance for any help you can give me!!

 

Morgan

Reply
Options

6017 Posts

10-29-2009

NC

17488 Signins

156043 Page Views

  • Posts: 6017
  • Registered: ‎10-29-2009
  • Location: NC
  • Views: 156043
  • Message 2 of 3

Re: T420s fingerprint reader connected but not detected when powered on

2015-07-06, 17:39 PM

It sounds to me like the fingerprint sensor itself is dying.  

 

The sensor actually has 2 modes.  There is one mode when the system is powered off (where green LED comes on, and you can swipe to power on).  Then there is another mode when the system is powered on, where the device is connected as USB so that Windows/software can talk to it.  In your case, sounds like the latter mode doesn't work anymore.  Unfortunately, I have heard of this problem before and there is not any solution except to replace it.

Reply
Options

2 Posts

07-04-2015

London

3 Signins

34 Page Views

  • Posts: 2
  • Registered: ‎07-04-2015
  • Location: London
  • Views: 34
  • Message 3 of 3

Re: T420s fingerprint reader connected but not detected when powered on

2015-07-06, 19:01 PM

Yeah this is the conclusion I have come to also. Looking at the fingerprint reader it looks like I can replace just the sensor and not the whole palm rest? Do you have a part number for just the sensor?

Reply
Forum Home

Community Guidelines

Please review our Guidelines before posting.

Learn More

Check out current deals!

Go Shop
X

Save