DTC P176A-87: Lost Communication with Fail Safe Signal (Gear Shift Control Module "A") Missing Message [10/2020 - 10/2023]: Procedure

1. Disconnect the hybrid vehicle control ECU connector.
2. Connect an oscilloscope between the hybrid vehicle control ECU connector terminals specified in the table below.
3. w/o Advanced Park:

   Turn the power switch on (IG) and measure the waveform.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a	Front view of wire harness connector (to Hybrid Vehicle Control ECU)
   *b	Waveform (Fail-safe signal)

   Tester Connection	Condition	Equipment Setting
   G92-25 (SBFS) - G92-6 (E1)	Power switch on (IG)	10 V/DIV., 20 ms./DIV.

   NOTE:

   Turning the power switch on (IG) with the connector disconnected causes other DTCs to be stored. Clear the DTCs after performing this inspection.

   HINT: 

   The waveforms differ when the shift control ECU is malfunctioning.

4. w/ Advanced Park:

   Turn the power switch on (IG) and measure the waveform.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a	Front view of wire harness connector (to Hybrid Vehicle Control ECU)
   *b	Waveform (Fail-safe signal)

   Tester Connection	Condition	Equipment Setting
   G166-12 (SBFS) - G166-15 (E1)	Power switch on (IG)	10 V/DIV., 20 ms./DIV.

   NOTE:

   Turning the power switch on (IG) with the connector disconnected causes other DTCs to be stored. Clear the DTCs after performing this inspection.

   HINT: 

   The waveforms differ when the shift control ECU is malfunctioning.

5. Turn the power switch off.
6. Reconnect the hybrid vehicle control ECU connector.

   Result

   Proceed to
   OK
   NG

Result: 

OK 

REPLACE HYBRID VEHICLE CONTROL ECU. Refer to  REMOVAL [10/2020 - 11/2021]  , or refer to  REMOVAL [11/2021 - 10/2022]  , or refer to  REMOVAL [10/2022 - 10/2023] 

Result: 

NG 

See step  2

1. Disconnect the G81 shift control ECU connector.
2. w/o Advanced Park:

   Disconnect the G92 hybrid vehicle control ECU connector.

3. w/ Advanced Park:

   Disconnect the G166 hybrid vehicle control ECU connector.

4. w/o Advanced Park:

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

   Standard Resistance (Check for Open)

   Tester Connection	Condition	Specified Condition
   G81-3 (SBFS) - G92-25 (SBFS)	Always	Below 1 Ω

   Standard Resistance (Check for Short)

   Tester Connection	Condition	Specified Condition
   G81-3 (SBFS) or G92-25 (SBFS) - Body ground and other terminals	Always	10 kΩ or higher

5. w/ Advanced Park:

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

   Standard Resistance (Check for Open)

   Tester Connection	Condition	Specified Condition
   G81-3 (SBFS) - G166-12 (SBFS)	Always	Below 1 Ω

   Standard Resistance (Check for Short)

   Tester Connection	Condition	Specified Condition
   G81-3 (SBFS) or G166-12 (SBFS) - Body ground and other terminals	Always	10 kΩ or higher

6. w/o Advanced Park:

   Reconnect the G92 hybrid vehicle control ECU connector.

7. w/ Advanced Park:

   Reconnect the G166 hybrid vehicle control ECU connector.

8. Reconnect the G81 shift control ECU connector.

   Result

   Proceed to
   OK
   NG

Result: 

OK 

REPLACE SHIFT CONTROL ECU. Refer to  REMOVAL [10/2020 - 11/2021]  , or refer to  REMOVAL [11/2021 - 10/2022]  , or refer to  REMOVAL [10/2022 - 10/2023] 

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR