DTC P0A78-73: Drive Motor "A" Inverter Actuator Stuck Closed [12/2019 - 11/2023]: Procedure

1. Check for DTCs.

   Powertrain > Hybrid Control > Trouble Codes 

   Result

   Result	Proceed to
   P0A78-73 only is output, or DTCs except the ones in the table below are also output.	A
   Any of the following DTCs are also output.	B

   Malfunction Content	Relevant DTC
   Insulation Malfunction	P1C7C-49	Hybrid/EV Battery Voltage System Isolation (A/C Area) Internal Electronic Failure
   	P1C7D-49	Hybrid/EV Battery Voltage System Isolation (Hybrid/EV Battery Area) Internal Electronic Failure
   	P1C7E-49	Hybrid/EV Battery Voltage System Isolation (Transaxle Area) Internal Electronic Failure
   	P1C7F-49	Hybrid/EV Battery Voltage System Isolation (Direct Current Area) Internal Electronic Failure
   	P1C80-49	Hybrid/EV Battery Voltage System Isolation (Rear Motor Area) Internal Electronic Failure

   HINT: 

   • P0A78-73 may be output as a result of the malfunctions indicated by the DTCs above.
     1. The chart above is listed in inspection order of priority.
     2. Check DTCs that are output at the same time by following the listed order. (The main cause of the malfunction can be determined without performing unnecessary inspections.)
2. Turn the ignition switch off.

Result: 

B 

GO TO DTC CHART (HYBRID CONTROL SYSTEM) 

Refer to DIAGNOSTIC TROUBLE CODE CHART [12/2019 - 09/2020] , or refer to DIAGNOSTIC TROUBLE CODE CHART [09/2020 - 10/2021] , or refer to DIAGNOSTIC TROUBLE CODE CHART [10/2021 - 11/2023]

Result: 

A 

See step  2

1. Check that the service plug grip is not installed.
   NOTE:

   After removing the service plug grip, do not turn the ignition switch on (READY), unless instructed by the repair information because this may cause a malfunction.

2. Disconnect the motor cable from the hybrid vehicle transaxle assembly.

   HINT: 

   Refer to REMOVAL [12/2019 - 10/2022] , or refer to REMOVAL [10/2022 - 11/2023]

3. Check the motor (MG2) for an interphase short using a milliohmmeter.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a	Motor Cable not connected (Hybrid Vehicle Transaxle Assembly)

   1. Using a milliohmmeter, measure the resistance according to the value(s) in the table below.

      HINT: 

      If the motor (MG2) temperature is high, the resistance will vary greatly from the specification. Therefore, measure the resistance at least 8 hours after the vehicle has been stopped.

      Standard Resistance

      Tester Connection	Condition	Specified Condition
      w1-1 (W) - w1-2 (U)	Ignition switch off	29.5 to 32.7 mΩ
      w1-2 (U) - w1-3 (V)	Ignition switch off	29.5 to 32.7 mΩ
      w1-1 (W) - w1-3 (V)	Ignition switch off	29.6 to 32.8 mΩ

      HINT: 

      To correct the variation of the measured resistance due to temperature, use the following formula to calculate the resistance at 20°C (68°F).

      1. R20 = Rt / {1 + 0.00393 X (T - 20)}

      The calculation is based on the following:

      1. R20: Resistance at 20°C (68°F) (mΩ)
      2. Rt: Measured resistance (mΩ)
      3. T: Temperature when the resistance is measured (°C)
4. Using a megohmmeter set to 500 V, measure the resistance according to the value(s) in the table below.
   NOTE:

   Be sure to set the megohmmeter to 500 V when performing this test. Using a setting higher than 500 V can result in damage to the component being inspected.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   w1-1 (W) - Body ground and shield ground	Ignition switch off	10 MΩ or higher
   w1-2 (U) - Body ground and shield ground	Ignition switch off	10 MΩ or higher
   w1-3 (V) - Body ground and shield ground	Ignition switch off	10 MΩ or higher

5. Connect the motor cable.

   Result

   Proceed to
   OK
   NG

Result: 

NG 

See step  5

Result: 

OK 

See step  3

Refer to REMOVAL [12/2019 - 10/2022] , or refer to REMOVAL [10/2022 - 11/2023]

Result

Result: 

NEXT 

See step  4

Refer to REMOVAL [12/2019 - 10/2022] , or refer to REMOVAL [10/2022 - 11/2023]

Result

Result: 

NEXT 

See step  8

Refer to REMOVAL [12/2019 - 10/2022] , or refer to REMOVAL [10/2022 - 11/2023]

Result

Result: 

NEXT 

See step  6

Refer to REMOVAL [12/2019 - 10/2022] , or refer to REMOVAL [10/2022 - 11/2023]

Result

Result: 

NEXT 

See step  7

Refer to REMOVAL [12/2019 - 10/2022] , or refer to REMOVAL [10/2022 - 11/2023]

Result

Result: 

NEXT 

See step  8

1. Check the other DTCs that were output together with DTC P0A78-73.

   Powertrain > Motor Generator > Trouble Codes 

   Result

   Relevant DTC
   P0A78-9E	Drive Motor "A" Inverter Stuck On
   P1C5D-19	Drive Motor "A" Inverter Circuit Current Above Threshold

   NOTE:

   DTC P0A78-73 is stored after DTCs P0A78-9E and/or P1C5D-19 are stored. After troubleshooting and repairing the malfunction which caused P0A78-73 to be stored, be sure to troubleshoot the other DTCs.

   Result

   Proceed to
   NEXT

Result: 

NEXT 

GO TO DTC CHART (MOTOR GENERATOR CONTROL SYSTEM)  . Refer to DIAGNOSTIC TROUBLE CODE CHART [12/2019 - 10/2021] , or refer to DIAGNOSTIC TROUBLE CODE CHART [10/2021 - 11/2023]