What was found
ON TAXI-IN WITH APU RUNNING AND ELECTRIC AVAILABLE APU GENERATORS WOULD NOT COME ONLINE. APU GEN VOLTAGE READ 0 (ZERO). GROUNDED - YES. OPERATED APU GERATION SYSTEM WITH NO DISCREPANCIES NOTED. CYCLED POWER SEVERAL TIMES BETWEEN APU AND ENGINES, ALL OPS NML. REPLACED P5-4 PANEL, AND PERFORMED INSTALLATION TEST, ALL TEST PASS. GROUND VERIFICATION SATISFACTORY. REF B737-900 AMM 24-21-51, 24-21-00,71-00-00, 49-11-00. ORIG SUBMISSION DATE: 12/19/2022