As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
"AUTO FAIL" AND ALTN LIGHT ON "AUTO FAIL" LIGHT GOES OFF WHEN PRESSURIZATION MODE SELECTOR SWITCH MOVED TO ALTN. VERIFIED NR 2 CABIN PRESSURE CONTROLLER SHOWED CONTROLLER FAILURE. REPLACED NR 2 CABIN PRESS CONTROLLER. REF MM 21 31 00. OPS CHECK GOOD.