DTC P176A-87: Lost Communication with Fail Safe Signal (Gear Shift Control Module "A") Missing Message [03/2017 - 05/2023]: Procedure

1. Disconnect the ECM connector.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a	Front view of wire harness connector (to ECM)
   *b	Waveform (Fail-safe signal)

2. Connect an oscilloscope between the ECM connector terminal specified in the table below and body ground.
3. Turn the engine switch on (IG) and measure the waveform.

   Item	Contents
   Terminal	SBFS - Body ground
   Equipment Setting	10 V/DIV., 20 ms./DIV.
   Condition	Engine switch on (IG)

   NOTE:

   Turning the engine 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. Turn the engine switch off.
5. Reconnect the ECM connector.

   Result

   Proceed to
   OK
   NG

Result: 

OK 

REPLACE ECM. Refer to  REMOVAL [03/2017 - 05/2023] 

Result: 

NG 

See step  2

1. Disconnect the P74 shift control ECU connector.
2. Disconnect the A58 ECM connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance (Check for Open)

   Tester Connection	Condition	Specified Condition
   P74-3 (SBFS) - A58-29 (SBFS)	Always	Below 1 Ω

   Standard Resistance (Check for Short)

   Tester Connection	Condition	Specified Condition
   P74-3 (SBFS) or A58-29 (SBFS) - Body ground and other terminals	Always	10 kΩ or higher

4. Reconnect the A58 ECM connector.
5. Reconnect the P74 shift control ECU connector.

   Result

   Proceed to
   OK
   NG

Result: 

OK 

REPLACE SHIFT CONTROL ECU. Refer to  REMOVAL [03/2017 - 05/2023] 

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR