Lexus RX (RX 350L, RX450h) 2016-2026 Repair Manual: Lost Communication with ECM / PCM (U0100,U0140,U0142,U0155,U1117)

Lexus RX (RX 350L, RX450h) 2016-2026 Repair Manual / Vehicle Interior / Theft Deterrent / Keyless Entry / Smart Access System With Push-button Start (for Start Function) / Lost Communication with ECM / PCM (U0100,U0140,U0142,U0155,U1117)

DESCRIPTION

These DTCs are stored when there is a CAN communication malfunction between the certification ECU (smart key ECU assembly), ECM, main body ECU (multiplex network body ECU) or combination meter assembly, and data from the option connector (bus buffer ECU) cannot be received.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	Note
U0100	Lost Communication with ECM / PCM	CAN communication malfunction between certification ECU (smart key ECU assembly) and ECM (1-trip detection logic*)	ECM	Turn the engine switch on (IG) and wait at least 10 seconds.
U0140	Lost Communication with Main Body ECU	CAN communication malfunction between certification ECU (smart key ECU assembly) and main body ECU (multiplex network body ECU) (1-trip detection logic*)	Main body ECU (multiplex network body ECU)	Always
U0142	Lost Communication with Main Body ECU	CAN communication malfunction between certification ECU (smart key ECU assembly) and main body ECU (multiplex network body ECU) (1-trip detection logic*)	Main body ECU (multiplex network body ECU)	Always
U0155	Lost Communication with Combination Meter	CAN communication malfunction between certification ECU (smart key ECU assembly) and combination meter assembly (1-trip detection logic*)	Combination meter assembly	Turn the engine switch on (IG) and wait at least 10 seconds.
U1117	Lost Communication with Accessory Gateway	Data from the option connector (bus buffer ECU) cannot be received	Connector and branch wire of sub bus 2 of option connector (bus buffer ECU) Internal malfunction of option connector (bus buffer ECU)	Turn the engine switch on (IG) and wait at least 10 seconds.

*: Only detected while a malfunction is present.

Vehicle Condition and Fail-safe Function when Malfunction Detected

DTC Code	Vehicle Condition when Malfunction Detected	Fail-safe Function when Malfunction Detected
U0100	There is no effect on vehicle behavior.	If the following conditions are met, it can be determined that the malfunction is not in the direct line (NE) but in the CAN communication system. When the engine switch is pressed, the system controls the engine based on the engine speed signal via direct line, causing the engine to stop cranking. When the engine switch is pressed and held, the system controls the engine based on the engine speed signal via direct line, causing the engine to stop cranking. If the following conditions are met, it can be determined that there is a malfunction in both the CAN communication system and the direct line (NE). When the engine switch is pressed, the engine stops cranking after 6 seconds. When the engine switch is pressed and held, the engine remains cranking for up to 30 seconds.
U0140 U0142	Doors cannot be locked or unlocked. The warning (wireless buzzer) does not sound.	-
U0155	The warning (meter buzzer) does not sound and no warning messages displayed on the multi-information display.	-
U1117	The engine cannot be started using the wireless remote control function.	-

Related Data List and Active Test Items

DTC No.	Data List and Active Test
U0100 U0140 U0142 U0155 U1117	-

DTC No.

Data List and Active Test

U0100

U0140

U0142

U0155

U1117

CAUTION / NOTICE / HINT

NOTICE:

When using the Techstream with the engine switch off, connect the Techstream to the DLC3 and turn a courtesy light switch on and off at intervals of 1.5 seconds or less until communication between the Techstream and the vehicle begins. Then select the vehicle type under manual mode and enter the following menus: Body Electrical / Smart Access. While using the Techstream, periodically turn a courtesy light switch on and off at intervals of 1.5 seconds or less to maintain communication between the Techstream and the vehicle.
After repair, confirm that no DTCs are output by performing "DTC Output Confirmation Operation".

HINT:

When the cable is disconnected and reconnected to the negative (-) battery terminal, the power source mode returns to the state it was in before the cable was disconnected.

PROCEDURE

1.	CHECK FOR DTC

(a) Check for DTCs and note any DTCs that are output.

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GO TO CAN COMMUNICATION SYSTEM (HOW TO PROCEED WITH TROUBLESHOOTING)

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Lexus RX (RX 350L, RX450h) 2016-2026 Repair Manual: Lost Communication with ECM / PCM (U0100,U0140,U0142,U0155,U1117)

System Voltage or GND Energization Malfunction (B228B)

Engine does not Start

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Lexus RX (RX 350L, RX450h) 2016-{YEAR} Owners Manual

Lexus RX (RX 350L, RX450h) 2016-{YEAR} Repair Manual