As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT ENG DUCT PRESSURE @ 5 PSI AT IDLE. GROUNDED - YES. ACCOMPLISHED TROUBLESHOOTING ON LEFT ENG PNEU SYS PER B737-900 AMM TASK 36-00-00-860-807 PROCEDURE C. STEPS 1 THRU 6. R & R HIGH STAGE REGULATOR & HIGH STAGE VLV. ACCOMPLISHED IDLE RUN OPS CK GOOD REFERENCED AMM 36-11-06 & 07.