As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER ENGINE START, ON MASTER RECALL CONT CAB ZONE TEMP LIGHT ILLUMINATES. EXTINGUISHES ON RESET. GROUNDED - YES. UNABLE TO DUPLICATE DEFECT - MASTER CAUTION RECALL SHOWS NO ZONE TEMP LIGHTS. BITE TEST OF PACK/ZONE TEMP CONTROLLERS NR 1 AND 2 SHOWS NO FAULTS AND VERIFY TEST PASSES ON BOTH WITH NO FAULTS. PERFORMED CABIN TEMPERATURE CONTROL AND INDICATION - OPERATIONAL TEST PER B737-800 AMM 21-61-00-700-807-002 - ALL TESTS PASS.