As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: WHEN LEVELING OFF AT FL3700 FROM CLIMB AT CONTINUOUS POWER, AS POWER THRUST IS RETARED CABIN CLIMBS AT 500-1000 FPM - CABIN AUTO FAIL DID NOT ILLUMINATED - SUSPECT BLEED ISSUE LEFT DUCT PSI ZERO PSI. REPLACED LEFT ENGINE PRECOOLER VALVE AND THE VALVE SENSOR AND ACCOMPLSHED A SATISFACTORY OPERATIONAL CHECK PER AMM 36-12-03.