Home >> Land Rover >> 2021 >> Defender 110 >> Repair and Diagnosis >> General Information >> Specifications Index >> Diagnostic Trouble Code Index DTC: Audio Amplifier Module (AAM) -- Defender/L663 >> Diagnostic Trouble Code Index - DTC: Audio Amplifier Module (AAM) (G2804413) >> Description And Operation >> Audio Amplifier Module (AAM) >> DTC U0400-81: Invalid data received - Invalid serial data received >> Possible Causes