As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AUTOPILOT COMMAND B BUTTON WILL NOT ILLUMINATE AUTOPILOT FUNCTIONS NORMALLY. ACFT GROUNDED. REPLACED MASTER CONTROL PANEL IAW AMM TASK 22-11-34-400-801/22-11-34-000-801. PERFORMED MASTER CONTROL PANEL INSTALLATION TEST IAW AMM TASK 22-11-34-74-801.