Hello Charles, We manages to solve the problem. It was just the firmware of the Dell Diagnostic Tool that was not up to date. (When doing firmware update in Lifecycle controller it was not selected automatically). After the update the error disappeared.  
Hello, I have two Dell R640 servers with the same components, except the motherboard. Here are the two DP/N I have: W23H8 and CRT1G. What are the differences between those two boards? In the server with the CRT1G motherboard, when I plug a PCIe card, and launch a quick diagnostic, I get this error :  I tried to swap several component with another server : risers, PCIe card, CPU. The error follows the slot the card is plugged in, in the server, but not in the other one.And the error appears only with two CPUs. It does not appear with one CPU on the motherboard. Any clues on the cause of the error ?
PowerEdge R640 Motherboard