As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING ENG RUN, #1 ENG BLEED WOULD NOT SHUT OFF. GROUNDED - YES. FOUND NO. 1 ENG BLEED AIR REGULATOR ELECTRICAL CONNECTOR DISCONNECTED. CONNECTED THE ELECTRICAL CONNECTOR TO THE N0. 1 ENG BLEED AIR REGULATOR REF B737-900 AMM 36-11-03-400-801 STEP 3. E. (6).