DTC U0291-87: Lost Communication with Gear Shift Control Module "B" Missing Message [10/2022 - ]: Procedure

WARNING: This page is about a different car, the 2025 Lexus RX 350h, 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

According to the display on the GTS, select "Health Check".

Check for DTCs.

Result

Result	Proceed to
No DTCs are output.	A
DTCs are output.	B

Post-procedure1

Turn the ignition switch off.

Result:

GO TO DTC CHART. Refer to DIAGNOSTIC TROUBLE CODE CHART [10/2022 - 10/2024] , or Refer to DIAGNOSTIC TROUBLE CODE CHART [10/2024 - ]

Result:

See step 2

CHECK DTC OUTPUT (HYBRID CONTROL)

Pre-procedure1

None.

Check for DTCs.

Powertrain > Hybrid Control > Trouble Codes

Result

Result	Proceed to
Only U0291-87 is output	A
U0291-87 and U1176-87 are output	B

Post-procedure1

Turn the ignition switch off.

Result:

SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT CONTROL ACTUATOR ECU) POWER SOURCE CIRCUIT FAILURE. Refer to ECU Power Source Circuit [10/2022 - 08/2023] , or refer to ECU Power Source Circuit [08/2023 - ]

Result:

See step 3

CHECK SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT CONTROL ACTUATOR ECU) (BAT1 TERMINAL VOLTAGE)

Pre-procedure1

Disconnect the shift control actuator assembly (shift control actuator ECU) connector.

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

Standard Voltage

Tester Connection	Condition	Specified Condition	Result
B57-8 (BAT1) - Body ground	Ignition switch off	11 to 14 V	V

HINT:

As there might be an intermittent malfunction, inspect the following items even if the measured voltage is as specified.

Installation condition of fuse(s) (before removing fuse(s)) (BATT circuit)
Fuse condition (before and after removing fuse(s)) (BATT circuit)
Connection condition of connectors (BATT circuit)
Wire harness condition (BATT circuit)
Wire harness condition (GND circuit)

Result

Proceed to
OK
NG

Post-procedure1

Reconnect the shift control actuator assembly (shift control actuator ECU) connector.

Result:

REPAIR OR REPLACE HARNESS OR CONNECTOR (SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT CONTROL ACTUATOR ECU) POWER SOURCE CIRCUIT)

Result:

See step 4

CHECK SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT CONTROL ACTUATOR ECU) (IGC1 TERMINAL VOLTAGE)

Pre-procedure1

Disconnect the shift control actuator assembly (shift control actuator ECU) connector.

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

Standard Voltage

Tester Connection	Condition	Specified Condition	Result
B56-5 (IGC1) - Body ground	Ignition switch off	11 to 14 V	V

HINT:

As there might be an intermittent malfunction, inspect the following items even if the measured voltage is as specified.

Installation condition of fuse(s) (before removing fuse(s)) (IGC1 circuit)
Fuse condition (before and after removing fuse(s)) (IGC1 circuit)
Connection condition of connectors (IGC1 circuit)
Wire harness condition (IGC1 circuit)
Wire harness condition (GND circuit)

Result

Proceed to
OK
NG

Post-procedure1

Turn the ignition switch off.
Reconnect the shift control actuator assembly (shift control actuator ECU) connector.

Result:

GO TO CAN COMMUNICATION SYSTEM. Refer to HOW TO PROCEED WITH TROUBLESHOOTING [10/2022 - 08/2023] , or refer to HOW TO PROCEED WITH TROUBLESHOOTING [08/2023 - ]

Result:

REPAIR OR REPLACE HARNESS OR CONNECTOR (SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT CONTROL ACTUATOR ECU) POWER SOURCE CIRCUIT)