Spoke to Dell (to get a price for the replacement system board) and they suggested trying the RAM in the other slot.  It worked!
A user has returned his laptop with the diagnostic LED indicating a RAM failure (2 amber and 4 white flashes) so I ordered a new stick of RAM from Crucial.  When it was replaced the diagnostic indicator pattern changed to 2 amber and 5 white which indicates invalid RAM. I purchased another stick this time with the same Hynix part code (HMA81GS6CJR8N-UH) as the faulty one. However, I get the same diagnostic code (2 amber and 5 white) indicating invalid RAM. Any thoughts on what might be causing this (other than a fault main board) or tests to complete?
5471 RAM issue