I have been informed from Dell support that this is a false positive and a firmware update will be released later this month to fix the issue.
XPS 13 9370 running Windows 10 Pro The Dell SupportAssist application picks up failure on PCI Express - Realtek PCIE CardReader, PCI Express Status Test WPE01-EH4 Does anyone else get this error? The cardreader itself appears to work fine. I tested with a microSDHC UHS-1 card and was able to read and write. Steps to reproduce: [URL]
XPS 13 9370 SupportAssist Failed - PCI Express - Realtek PCIE CardReader, PCI 
Express Status Test