BIOS dump ThinkPad T450 MiniPro TL866

[rumpumpel1]

Hi,

I've bought a cheap programmer (MiniPro TL866) to read and wrtite BIOS images from ThinkPads.
I'm using the ICSP port, so I don't have to desolder the BIOS chip.

This was working with a X240 and a T440p. But it did not work with a T450. The MiniPro was not even able to read the chip Id.
After desoldering the chip, I could read and write to the chip, so it was not the fault of the chip.
I also tried to use Vcc from the Mainboard instead from the MiniPro, but there was no difference.

So what could be the reason that this procedure does not work with T450?