DTC P178A-14: Gear Shift Control Module "B" Wake-up Circuit Short to Ground or Open [11/2021 - ]: Procedure
WARNING: This page is about a different car, the 2025 Lexus NX 350h, 2024 Lexus NX 350h, 2023 Lexus NX 350h, and 2022 Lexus NX 350h. However, it is still accessible from the selected car via links, so may be relevant.
- CHECK HARNESS AND CONNECTOR (WAKE TERMINAL VOLTAGE)
Pre-procedure1
- Disconnect the B78 shift control actuator assembly (shift actuator ECU) connector.
- Turn the ignition switch to ON.NOTE:
Turning the ignition switch to ON with the connector disconnected causes other DTCs to be stored. Clear the DTCs after performing this inspection.
Procedure1
- Measure the voltage according to the value(s) in the table below.
Standard Voltage
Tester Connection Condition Specified Condition B78-5 (WAKE) - Body ground Ignition switch ON 11 to 14 V Result
Proceed to OK NG Post-procedure1
- Turn the ignition switch off.
- Connect the shift control actuator assembly (shift actuator ECU) connector.
Result:
OK
REPLACE SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU). Refer to REMOVAL [11/2021 - ]
Result:
NG
See step 2
- CHECK HARNESS AND CONNECTOR (SHIFT ACTUATOR ECU - SHIFT CONTROL ECU)
Pre-procedure1
- Disconnect the B78 shift control actuator assembly (shift actuator ECU) connector.
- Disconnect the D39 transmission floor shift assembly (shift control ECU) connector.
Procedure1
- Measure the resistance according to the value(s) in the table below.
Standard Resistance
Tester Connection Condition Specified Condition B78-5 (WAKE) - D39-5 (WAKE) Always Below 1 Ω B78-5 (WAKE) or D39-5 (WAKE) - Body ground and other terminals Always 10 kΩ or higher Result
Proceed to OK NG Post-procedure1
- Connect the transmission floor shift assembly (shift control ECU) connector.
- Connect the shift control actuator assembly (shift actuator ECU) connector.
Result:
OK
REPLACE TRANSMISSION FLOOR SHIFT ASSEMBLY (SHIFT CONTROL ECU). Refer to REMOVAL [11/2021 - ]
Result:
NG
REPAIR OR REPLACE HARNESS OR CONNECTOR