DTC P178A-14: Gear Shift Control Module "B" Wake-up Circuit Short to Ground or Open [09/2023 - ]: Procedure
WARNING: This page is about a different car, the 2024 Lexus TX 500h. 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 C64 shift actuator ECU (shift control actuator assembly) 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.
- Measure the voltage according to the value(s) in the table below.
Standard Voltage
Tester Connection Condition Specified Condition Result C64-5 (WAKE) - Body ground Ignition switch ON 11 to 14 V V Result
Proceed to OK NG
Post-procedure1
- Turn the ignition switch off.
- Connect the shift actuator ECU (shift control actuator assembly) connector.
Result:
OK
REPLACE SHIFT ACTUATOR ECU (SHIFT CONTROL ACTUATOR ASSEMBLY). Refer to REMOVAL [09/2023 - ]
Result:
NG
See step 2
- CHECK HARNESS AND CONNECTOR (SHIFT ACTUATOR ECU - SHIFT CONTROL ECU)
Pre-procedure1
- Disconnect the C64 shift actuator ECU (shift control actuator assembly) connector.
- Disconnect the D25 shift control ECU (transmission floor shift assembly) connector.
- Measure the resistance according to the value(s) in the table below.
Standard Resistance
Tester Connection Condition Specified Condition Result C64-5 (WAKE) - D25-5 (WAKE) Always Below 1 Ω Ω C64-5 (WAKE) or D25-5 (WAKE) - Body ground and other terminals Always 10 kΩ or higher kΩ Result
Proceed to OK NG
Post-procedure1
- Connect the shift control ECU (transmission floor shift assembly) connector.
- Connect the shift actuator ECU (shift control actuator assembly) connector.
Result:
OK
REPLACE SHIFT CONTROL ECU (TRANSMISSION FLOOR SHIFT ASSEMBLY). Refer to REMOVAL [09/2023 - ]
Result:
NG
REPAIR OR REPLACE HARNESS OR CONNECTOR