As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING ENGINE RUN PREPARING TO TAXI, #1 IDG SOURCE LT ILLUMINATED. GROUNDED - YES. REMOVED AND REPLACED #1 IDG REF B737-900 AMM 24-11-11/401. OPS CHECKED GOOD. A/C RETURNED TO ORIGINAL CONFIGURATION. RE-LAMPED GEN DRIVE AND GEN OFF BUS LIGHTS.