As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
OPENING OF APU ISOLATION VALVE CAUSES ENGINE NR 2 START VALVE TO OPEN. GROUNDED-YES. REMOVED AND REPLACED NR 2 ENGINE START VALVE, REF B737-900 AMM 80-11-03. OPERATIONS/LEAK CHECK GOOD. PERFORMED B737-900 FIM 80-07 TASK 802 AND FOUND DEBRIS IN THE STARTER MAGNETIC PLUG. REMOVED AND REPLACED THE NR 2 ENGINE STARTER, REF AMM 80-11-01. OPERATIONS CHECK NORMAL. LEAK CHK NORMAL.