As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AUTO FAIL AND ALTN LIGHTS ILLUMINATED DURING FLIGHT AT FL400 APPROX 40 MIN INTO FLIGHT - NON ETOPS VERIFICATION NOT SUCCESSFUL. GROUNDED - YES. REMOVED AND REPLACED AFT OUTFLOW VALVE ASSEMBLY IAW B737-9MAX-AMM 21-31-03-000-801 & 21-31-03-400-801 OPS CHECKS GOOD.