2012 Mac Pro - Diagnostic LED CPUA CPUB flash red when mains power switched on. Boots up fine though.

Hi everyone,

I have a 2012 Mac Pro.

Specs as follows:

Two 2.66GHz 6-Core Intel Xeon “Westmere” (12 cores)

32GB RAM (8 x 4GB) - from OWC

ATI Radeon HD 5770 1GB

2 x 1TB 7200RPM SATA 3Gb/s HDD

The problem is that the CPUA and CPUB diagnostic LED flashes red one time when I switch on the power from the mains. When I switch on the power on the Mac Pro it boots up fine.

When I press the diagnostic led button, the only LED that lights up is the 5v Stby yellow LED.