Home >> Land Rover >> 2021 >> Defender 110 >> Repair and Diagnosis >> Quick Lookups >> Common Specs & Procedures >> Diagnostic Trouble Code Index DTC: Transmission Control Module (TCM) -- Defender/L663 >> Diagnostic Trouble Code Index - DTC: Transmission Control Module (TCM) (G3187879) >> Description And Operation >> Transmission Control Module (TCM) - 8HP70/45 Transmissions >> DTC U0028-88: Vehicle Communication Bus A - Bus off >> Possible Causes