As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHEN VNAV SWITCH IS PRESSED GREEN LIGHT IN SWITCH ILLUMINATES AND "VNAV"APPEARS IN WHITE ON FMA AT TOP OF PFD'S. AFTER 3-10 SECONDS VNAV MODE TURNS OFF WITHOUT PILOT ACTION. GROUNDED - YES. ACCOMPLISH MAX DISPLAY SYS - OPERATIONAL TEST REF TASK 31-65-00-710-801 - OK. REBOOTED A/C PWR - OPS CK OK.