DTC P179F-00: Gear Shift Actuator "B" Performance [11/2021 - ]: Procedure

WARNING: This page is about a different car, the 2025 Lexus NX 350, 2024 Lexus NX 350, 2023 Lexus NX 350, and 2022 Lexus NX 350. However, it is still accessible from the selected car via links, so may be relevant.

CHECK VEHICLE CONDITION

Check for removal and installation history of the shift control actuator assembly (shift actuator ECU).

HINT:

If the shift control actuator assembly (shift actuator ECU) has been replaced or removed, make sure to perform actuator position learning. Check for removal and installation history as this DTC may be stored if the learning has not been completed.

Result

Result	Proceed to
History exists	A
No history	B

Result:

See step 5

Result:

See step 2

CLEAR DTC

Pre-procedure1

Turn the ignition switch to ON.
Procedure1

Clear the DTCs.

Powertrain > Transmission > Clear DTCs

Result

Proceed to
NEXT

Post-procedure1

Turn the ignition switch off.
Disconnect the GTS.
Leave the vehicle as is for 60 seconds or more.
NOTE:
- Do not connect the GTS.
- Do not depress the brake pedal.
- Do not open/close any of the doors.

Result:

See step 3

PERFORM UTILITY (ACT POSITION LEARNING)

Pre-procedure1

Turn the ignition switch to ON.
Procedure1

Perform ACT Position Learning.

HINT:

Refer to UTILITY [11/2021 - ]

Powertrain > Transmission > Utility

Tester Display
ACT Position Learning

Result

Proceed to
NEXT

Post-procedure1

Turn the ignition switch off.

Result:

See step 4

CHECK DTC OUTPUT

Pre-procedure1

Start the engine.
With the brake pedal depressed, perform a shift operation then change the shift state to N.
With the brake pedal depressed, perform a shift operation then change the shift state to R.
With the brake pedal depressed, perform a shift operation then change the shift state to D.
Press the P position switch to change the shift state to P.
Procedure1

Check for DTCs.

Powertrain > Transmission > Trouble Codes

Result

Result	Proceed to
P179F-00 is not output	A
P179F-00 is output	B

Post-procedure1

Turn the ignition switch off.

Result:

END

Result:

See step 5

CHECK DTC OUTPUT (TRANSMISSION)

Pre-procedure1

Turn the ignition switch to ON.
Procedure1

Check if DTCs are output.

Powertrain > Transmission > Trouble Codes

Result

Result	Proceed to
No DTCs in the table below are output	A
P179F-00 and any DTCs in the table below are output	B

Relevant DTC
P1790-14	Gear Shift Actuator "A" Supply Voltage "A" Circuit Short to Ground or Open
P1796-14	Gear Shift Actuator "B" Supply Voltage "A" Circuit Short to Ground or Open
U1176-87	Lost Communication with Gear Shift Control Module "A" (ch2) Missing Message
U0291-00	Lost Communication with Gear Shift Control Module "B" (System 2) Missing Message
P1789-00	Lost Communication with Gear Shift Control Module "A" from "B" (Sub CPU) Missing Message
P1753-87	Lost Communication with Gear Shift Control Module "B" (Local-CAN) Missing Message
U1170-00	Lost Communication with Brake System Control Module (Gear Shift Control Module "A")
P179C-49	Gear Shift Actuator "A" Control Circuit Internal Electronic Failure
P179D-49	Gear Shift Actuator "B" Control Circuit Internal Electronic Failure
P18B2-00	Gear Shift Control Module "B" Motor Angle Sensor "A" Performance
P18B6-00	Gear Shift Control Module "B" Motor Angle Sensor "B" Performance
P18B5-62	Gear Shift Actuator "A" Phase U-V-W Current Sensor Signal Compare Failure
P18B9-62	Gear Shift Actuator "B" Phase U-V-W Current Sensor Signal Compare Failure
P0914-2B	Gear Shift Position Circuit "A" Range/Performance Signal Cross Coupled
P091A-2B	Gear Shift Position Circuit "B" Range/Performance Signal Cross Coupled
P1779-49	Gear Shift Control Module Backup Power Supply Internal Electronic Failure
P1779-96	Gear Shift Control Module Backup Power Supply Component Internal Failure
P177A-87	Lost Communication with Gear Shift Control Module Backup Power Supply Missing Message

Post-procedure1

Turn the ignition switch off.

Result:

GO TO DTC CHART. Refer To DIAGNOSTIC TROUBLE CODE CHART [11/2021 - ]

for Automatic Transaxle System: Refer to DIAGNOSTIC TROUBLE CODE CHART [11/2021 - 03/2024] , or refer to DIAGNOSTIC TROUBLE CODE CHART [03/2024 - ]

for Electronic Shift Lever System: Refer to DIAGNOSTIC TROUBLE CODE CHART [11/2021 - ]

Result:

See step 6

INSPECT BATTERY TERMINAL (CONTACT PROBLEM)

Check the connection of the battery terminal.

The battery is connected securely and there are no contact problems.

HINT:

Perform an inspection with consideration of a power supply voltage interruption due to a loose terminal, poor connection, etc.

Result

Proceed to
OK
NG

Result:

CONNECT SECURELY

Result:

See step 7

CHECK HARNESS AND CONNECTOR (INTEGRATION CONTROL SUPPLY (INTEGRATED CAPACITOR) - SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU))

Pre-procedure1

Disconnect the B77 shift control actuator assembly (shift actuator ECU) connector.
Turn the ignition switch to ON.
Procedure1

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

Standard Voltage

Tester Connection	Condition	Specified Condition
B77-8 (BUB1) - Body ground	Ignition switch ON	8 to 14 V
B77-6 (MA2) - Body ground	Ignition switch ON	11 to 14 V

Result

Proceed to
OK
NG

NOTE:

As other DTCs will be stored when the ignition switch is turned to ON with the connector disconnected, be sure to clear the DTCs after the inspection.

Post-procedure1

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

Result:

See step 9

Result:

See step 8

INSPECT AUTOMATIC TRANSAXLE ASSEMBLY (STUCK/FREE SPINNING OFF PARKING LOCK SHAFT)

Check that the parking lock shaft.

Refer to ON-VEHICLE INSPECTION [11/2021 - ]

The parking lock shaft is not stuck, and moves reasonably smoothly to each shift position.

Result

Proceed to
OK
NG

Result:

REPLACE SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU). Refer to REMOVAL [11/2021 - ]

Result:

REPLACE AUTOMATIC TRANSAXLE ASSEMBLY. Refer to REMOVAL [11/2021 - 03/2022] , or refer to REMOVAL [03/2022 - 03/2024] , or refer to REMOVAL [03/2024 - ]

CHECK HARNESS AND CONNECTOR (INTEGRATION CONTROL SUPPLY (INTEGRATED CAPACITOR) - SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU))

Pre-procedure1

Disconnect the B77 shift control actuator assembly (shift actuator ECU) connector.
Disconnect the G102 integration control supply (integrated capacitor) connector.
Procedure1

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

Standard Resistance

Tester Connection	Condition	Specified Condition
B77-8 (BUB1) - G102-9 (BUAE)	Always	Below 1 Ω
B77-6 (MA2) - G102-19 (BUA)	Always	Below 1 Ω
B77-8 (BUB1) or G102-9 (BUAE) - Body ground and other terminals	Always	10 kΩ or higher
B77-6 (MA2) or G102-19 (BUA) - Body ground and other terminals	Always	10 kΩ or higher

Result

Proceed to
OK
NG

Post-procedure1

Connect the integration control supply (integrated capacitor) connector.
Connect the shift control actuator assembly (shift actuator ECU) connector.

Result:

REPAIR OR REPLACE HARNESS OR CONNECTOR

Result:

See step 10

CHECK HARNESS AND CONNECTOR (SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU) - BODY GROUND)

Pre-procedure1

Disconnect the B77 shift control actuator assembly (shift actuator ECU) connector.
Procedure1

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

Standard Resistance

Tester Connection	Condition	Specified Condition
B77-7 (E02) - Body ground	Always	Below 1 Ω

Result

Proceed to
OK
NG

Post-procedure1

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

Result:

REPLACE SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU). Refer to REMOVAL [11/2021 - ]

Result:

REPAIR OR REPLACE HARNESS OR CONNECTOR