DTC U1002: Lost Communication with Gateway Module (Main Body ECU) [11/2017 - 03/2019]: Description

The main body ECU (multiplex network body ECU) will store this DTC when no signals can be received from the ECUs that have been memorized as those that are connected to sub bus 1.
When the main body ECU (multiplex network body ECU) receives a response signal from the ECUs connected to sub bus 1, the main body ECU (multiplex network body ECU) recognizes and memorizes that the ECU is connected to sub bus 1. Based on this memorized data, the main body ECU (multiplex network body ECU) monitors for malfunctions in the ECUs connected to sub bus 1 when communicating with those ECUs. If the main body ECU (multiplex network body ECU) cannot receive response signals from the ECUs that have been memorized as those connected to sub bus 1, the main body ECU (multiplex network body ECU) determines that a malfunction exists.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	Note
U1002	Lost Communication with Gateway Module (Main Body ECU)	The main body ECU (multiplex network body ECU) cannot receive signals from all ECUs that have been memorized as those connected to sub bus 1.	Open or short in sub bus 1 main lines or connector Short in sub bus 1 branch lines or connector Main body ECU (multiplex network body ECU) Outer mirror control ECU assembly (for driver side) (w/ Seat Position Memory System) Outer mirror control ECU assembly (for front passenger side) (w/ Seat Position Memory System) Position control ECU and switch assembly LH Position control ECU and switch assembly RH Multiplex tilt and telescopic ECU Headlight light control ECU sub-assembly LH (for Triple Beam Headlight) Open or short in No. 3 CAN junction connector Open or short in No. 5 CAN junction connector Open or short in No. 1 CAN junction terminal	HINT: The main body ECU (multiplex network body ECU) stores DTCs when it detects a communication stop or network communication error for ECUs connected to sub bus 1.

HINT:

This diagnostic procedure is for when DTC U1002 is output by the main body ECU (multiplex network body ECU) (Techstream display: Main Body).