As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: AN EMERGENCY WAS DECLARED DUE TO: ON CLIMB OUT TRIED TO ENGAGE AUTO PILOT A AND IT WOULD NOT ENGAGE. SWITCHED TO CHANNEL B WITH THE SAME RESULT; AIRCRAFT AIR INTERRUPTED BACK TO AND LANDED SAFELY AT ORD. TROUBLESHOT SYSTEM. NO FAULTS NOTED. ACCOMPLISHED FIM 22-11-00-810-801. ALL TESTS PASS NORMAL.