As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING PASSING 3000' WHEN PACKS WERE TURNED ON DUCT PRESS LOW LIGHT ILLUMINATED. DUCT PRESS 9 PSI. ENGINE BLEED VALVES 2, 3 AND 4 OPEN. REMOVED AND REPLACED NR 4 PRESS RELIEF VALVE. LEAK CHECKED COMPLIED WITH, NO DEFECTS AT THIS TIME REF AMM 71-00-00.