As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CLIMB POWER CLIMBING THRU 16000 RECEIVED AIR MANF 2 FAIL SYSTEM SELF PROTECTED. RETURNED TO GATE. FOUND AFT CARGO COMPARTMENT HEAT PRESS REG VALVE FAILED IN THE OPEN POSTION. REMOVED AND REPLACED AFT CARGO COMPARTMENT HEAT PRESS REG VALVE IAW AMM 21-41-15-4. OPS AND LEAK CHECKS NORMAL PERFORMED DECAY CHECK AND TEST PASSES.