P1603 Lexus ECU-TCU Communication Error

Possible causes

– Faulty Transaxle Control Module(TCM) or Engine Control Module(ECM)
– Transaxle Control Module(TCM) to Engine Control Module(ECM) harness is open or shorted
– Transaxle Control Module(TCM) to Engine Control Module(ECM) circuit poor electrical connection

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

P1603 Lexus Description

A communication line exists between the Engine Control Module(ECM) and the Transaxle Control Module(TCM). The communication is through a Control Area Network(CAN). Without CAN communication, an independent pin and wiring is needed to receive a sensor information from a ECM. The more information to be communicated, the more wirings is required. In case of CAN communication type, all the information need to be communicated among control modules such as ECM and TCM use CAN lines.