DTC U0100: Lost Communication with ECM / PCM; DTC U0140: Lost Communication with Main Body ECU; DTC U0142: Lost Communication with Main Body ECU; DTC U0155: Lost Communication with Combination Meter [06/2018 - ]: Description

WARNING: This page does not describe the selected car, but rather 10 other vehicles, including the 2024 Lexus ES 350, 2024 Lexus ES 250, 2023 Lexus ES 350, 2023 Lexus ES 250, and 2022 Lexus ES 350. However, it is still accessible from the selected car via links, so may be relevant.

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	DTC Output Confirmation Operation: 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)	DTC Output Confirmation Operation: 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)	DTC Output Confirmation Operation: 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	DTC Output Confirmation Operation: 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.	-

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.

RELATED DATA LIST AND ACTIVE TEST ITEMS

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