P1605 Chevrolet Automatic Transmission Communication
– Faulty Transmission Control Module (TCM)
– Harness is open or shorted between (TCM) and Engine Control Module (ECM)
– Poor circuit electrical connection between (TCM) and (ECM)
The malfunction information related to Automatic Transmission is transferred through the line circuit from Transmission control module (TCM) to Engine Control Module (ECM).