As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT RETURNED TO PLATFORM DUE TO MACH SPEED TRIM MESSAGE ILLUMINATION. THE BITE TEST ON P61 ADC WAS ACCOMPLISHED AND LIGHT ILLUMINATION IN OVERHEAD P11. FLIGHT CONTROLS TEST WAS ACCOMPLISHED AND LT ELEV PCU MESSAGE ILLUMINATED. THE MESSAGE APPEARED ONLY WHEN THE THREE HYDRAULIC SYSTEMS ARE OPERATIN. THE LT ELEV-PCU MESSAGE IS DEFERRED BY MEL 27-21-2.