DTC U0291-00: Lost Communication with Gear Shift Control Module "B" (System 2) Missing Message [08/2023 - ]: Procedure

WARNING: This page is about a different car, the 2025 Lexus RX 450h+, 2025 Lexus RX 350h, 2024 Lexus RX 450h+, 2024 Lexus RX 350h, and 2023 Lexus RX 350h. However, it is still accessible from the selected car via links, so may be relevant.

CHECK DTC OUTPUT (HEALTH CHECK)

Pre-procedure1

Turn the ignition switch to ON.

Using the GTS, perform a Health Check.

Result

Result	Proceed to
U0291-00 only is output	A
U0291-00 and other DTCs are output	B

Post-procedure1

Turn the ignition switch off.

Result:

GO TO DTC CHART. Refer to DIAGNOSTIC TROUBLE CODE CHART [08/2023 - ]

Result:

See step 2

CHECK FOR SHORT TO GROUND IN CAN BUS LINE (ECU CONNECTED)

Pre-procedure1

Disconnect the cable from the negative (-) auxiliary battery terminal.

Measure the resistance according to the value(s) in the table below.

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

*a	Component with harness connected (Transmission Floor Shift Assembly (Shift Control ECU))

Standard Resistance (Check for Short)

Tester Connection	Condition	Specified Condition	Result
C35-21 (CA3H) or C35-6 (CA3L) - Body ground	Cable from negative (-) auxiliary battery terminal disconnected	200 Ω or higher	Ω

Result

Proceed to
OK
NG

Post-procedure1

Connect the cable to the negative (-) auxiliary battery terminal.

Result:

See step 5

Result:

See step 3

CHECK FOR OPEN AND SHORT TO OTHER TERMINALS IN CAN BUS LINE (SHIFT CONTROL ECU - SHIFT ACTUATOR ECU)

Pre-procedure1

Disconnect the cable from the negative (-) auxiliary battery terminal.
Disconnect the B56 shift control actuator assembly (shift actuator ECU) connector.

Measure the resistance according to the value(s) in the table below.

Standard Resistance (Check for Open)

Tester Connection	Condition	Specified Condition	Result
B56-4 (CA3H) - B56-3 (CA3L)	Cable from negative (-) auxiliary battery terminal disconnected	54 to 69 Ω	Ω

Result

Proceed to
OK
NG

Post-procedure1

Connect the shift control actuator assembly (shift actuator ECU) connector.
Connect the cable to the negative (-) auxiliary battery terminal.

Result:

REPLACE SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU). Refer to REMOVAL [08/2023 - ]

Result:

See step 4

CHECK HARNESS AND CONNECTOR (SHIFT CONTROL ECU - SHIFT ACTUATOR ECU)

Pre-procedure1

Disconnect the C35 transmission floor shift assembly (shift control ECU) connector.
Disconnect the B56 shift control actuator assembly (shift actuator ECU) connector.
Disconnect the C59 hybrid vehicle control ECU connector.
Disconnect the z34 battery voltage sensor connector. (for THS-HEV model)
Disconnect the H124 electric vehicle charger assembly connector. (for PHEV model)
Disconnect the o5 battery ECU assembly connector. (for PHEV model)
Connect the SST. (for PHEV model)
HINT:

Refer to Instructions for Connecting SST [08/2023 - ]

Measure the resistance according to the value(s) in the table below.

Standard Resistance

Tester Connection	Condition	Specified Condition	Result
C35-21 (CA3H) - B56-4 (CA3H)	Always	Below 1 Ω	Ω
C35-6 (CA3L) - B56-3 (CA3L)	Always	Below 1 Ω	Ω
B56-4 (CA3H) - B56-3 (CA3L)	Always	1 MΩ or higher	MΩ
C35-21 (CA3H) - C35-6 (CA3L)	Always	1 MΩ or higher	MΩ

Result

Proceed to
OK
NG

Post-procedure1

Disconnect the SST. (for PHEV model)
Connect the battery ECU assembly connector. (for PHEV model)
Connect the electric vehicle charger assembly connector. (for PHEV model)
Connect the battery voltage sensor connector. (for THS-HEV model)
Connect the hybrid vehicle control ECU connector.
Connect the shift control actuator assembly (shift actuator ECU) connector.
Connect the shift control actuator assembly (shift actuator ECU) connector.

Result:

GO TO CAN COMMUNICATION SYSTEM. Refer to HOW TO PROCEED WITH TROUBLESHOOTING [08/2023 - ]

Result:

REPAIR OR REPLACE HARNESS OR CONNECTOR IN CAN BUS LINE (SHIFT CONTROL ECU - SHIFT ACTUATOR ECU)

CHECK FOR SHORT TO GROUND IN CAN BUS LINE (SHIFT ACTUATOR ECU DISCONNECTED)

Pre-procedure1

Disconnect the cable from the negative (-) auxiliary battery terminal.
Disconnect the B56 shift control actuator assembly (shift control actuator ECU) connectors.

Measure the resistance according to the value(s) in the table below.

*a	Component with harness connected (Transmission Floor Shift Assembly (Shift Control ECU))

Standard Resistance

Tester Connection	Condition	Specified Condition	Result
C35-21 (CA3H) or C35-6 (CA3L) - Body ground	Cable from negative (-) auxiliary battery terminal disconnected	200 Ω or higher	Ω

Result

Proceed to
OK
NG

Post-procedure1

Reconnect the shift control actuator assembly (shift control actuator ECU) connector.
Connect the cable to the negative (-) auxiliary battery terminal.

Result:

REPLACE SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU). Refer to REMOVAL [08/2023 - ]

Result:

See step 6

CHECK FOR SHORT TO GROUND IN CAN BUS LINE (SHIFT CONTROL ECU DISCONNECTED)

Pre-procedure1

Disconnect the cable from the negative (-) auxiliary battery terminal.
Disconnect the C35 transmission floor shift assembly (shift control ECU) connector.

Measure the resistance according to the value(s) in the table below.

Standard Resistance

Tester Connection	Condition	Specified Condition	Result
C35-21 (CA3H) or C35-6 (CA3L) - Body ground	Cable from negative (-) auxiliary battery terminal disconnected	200 Ω or higher	Ω

Result

Proceed to
OK
NG

Post-procedure1

Reconnect the transmission floor shift assembly (shift control ECU) connector.
Connect the cable to the negative (-) auxiliary battery terminal.

Result:

REPLACE TRANSMISSION FLOOR SHIFT ASSEMBLY (SHIFT CONTROL ECU). Refer to REMOVAL [10/2022 - ]

Result:

REPAIR OR REPLACE HARNESS OR CONNECTOR IN CAN BUS LINE (SHIFT CONTROL ECU - SHIFT ACTUATOR ECU)