DTC P0A78-121: Drive Motor "A" Inverter Performance: Procedure

1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG).
3. Enter the following menus: Powertrain / EV Battery / Trouble Codes.
4. Check if DTCs related to the EV battery system are output.

   Result

   Result	Proceed to
   Only P0A78-121 is output, or DTCs other than the ones in the table below are also output.	A
   Any of the following DTCs are also output.	B

   DTC No.	Relevant Diagnosis
   P1A61-123	EV Battery No. 1 Cell Low Voltage Stack "B"
   P1A64-123	EV Battery No. 1 Cell Low Voltage Stack "C"
   P1A71-123	EV Battery No. 2 Cell Low Voltage Stack "B"
   P1A74-123	EV Battery No. 2 Cell Low Voltage Stack "C"
   P31AB-123	EV Battery No. 1 Cell Low Voltage Stack "A"
   P31AE-123	EV Battery No. 2 Cell Low Voltage Stack "A"

   HINT: 

   P0A78-121 may be set due to a malfunction which also causes DTCs in the preceding table to be set. In this case, first troubleshoot the output DTCs in the preceding table. Then, perform a test to attempt to reproduce the problems, and check that no DTCs are output.

5. Turn the power switch off.

B → See step   29 

A: Go to next step 

1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG).
3. Enter the following menus: Powertrain / EV / Trouble Codes.
4. Check if DTCs related to the EV control system are output.

   Result

   Result	Proceed to
   Only P0A78-121 is output, or DTCs other than the ones in the table below are also output.	A
   Any of the following DTCs including pending DTCs are also output.	B

   DTC No.	Relevant Diagnosis
   P0A1A (all INF codes)*1	Generator Control Module
   P0A1B (all INF codes)*1	Drive Motor "A" Control Module
   P0A1D (all INF codes)*1	EV Control Module
   P0A3F-243	Drive Motor "A" Position Sensor Circuit
   P0A40-500	Drive Motor "A" Position Sensor Circuit Range/Performance
   P0A41-245	Drive Motor "A" Position Sensor Circuit Low
   P0A60 (all INF codes)*1	Drive Motor "A" Phase V Current
   P0A63 (all INF codes)*1	Drive Motor "A" Phase W Current
   P0A78-113, 128, 266, 267, 284, 286, 287, 306, 505, 506, 565, 586, 806, 807, 808	Drive Motor "A" Inverter Performance
   P0A90-509	Drive Motor "A" Performance
   P0A94-585, 587, 589, 590	Inverter Performance
   P0ADB-227	EV Battery No. 1 Positive Contactor Control Circuit Low
   P0ADC-226	EV Battery No. 1 Positive Contactor Control Circuit High
   P0ADF-229	EV Battery Negative Contactor Control Circuit Low
   P0AE0-228	EV Battery Negative Contactor Control Circuit High
   P0C76-523	EV Battery System Discharge Time Too Long
   P3004-131, 803	High Voltage Power Resource
   P3322-368	EV Battery No. 2 Positive Contactor Control Circuit Low
   P3323-367	EV Battery No. 2 Positive Contactor Control Circuit High

   HINT: 

   • *1: If any INF codes are output for this DTC, refer to the corresponding diagnostic procedure.
   • P0A78-121 may be set due to a malfunction which also causes DTCs in the preceding table to be set. In this case, first troubleshoot the output DTCs in the preceding table. Then, perform a test to attempt to reproduce the problems, and check that no DTCs are output.
5. Turn the power switch off.

B → See step   25 

A: Go to next step 

NG → CONNECT SECURELY 

OK: Go to next step 

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

NG → See step   17 

OK: Go to next step 

B → REPLACE MALFUNCTIONING PARTS 

C → CONNECT SECURELY 

A: Go to next step 

NG → See step   22 

OK: Go to next step 

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

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

2. Remove the upper inverter cover sub-assembly from the inverter with converter assembly.
   Fig 1: Identifying Upper Inverter Cover Sub-Assembly Bolts

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
3. Check that the bolts for the frame wire are tightened to the specified torque, the frame wire is connected securely, and there are no contact problems.
   Fig 2: Identifying Frame Wire Bolts

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   Specified Condition

   Bolt A 

   8.0 N*m (82 kgf*cm, 71 in.*lbf)

   Bolt B 

   9.2 N*m (94 kgf*cm, 81 in.*lbf)

   NOTE:

   • Make sure that the tightening torque of the bolt A is between 6.4 and 9.6 N*m (65 and 98 kgf*cm, 57 and 85 in.*lbf).
   • Make sure that the tightening torque of the bolt B is between 6.4 and 12 N*m (65 and 122 kgf*cm, 57 and 106 in.*lbf).
4. Disconnect the frame wire from the inverter with converter assembly.
5. Check for arc marks at the bolts and terminals for the frame wire.

   Result

   Result		Proceed to
   The terminals are connected securely and there are no contact problems.	There are no arc marks.	A
   The terminals are not connected securely and there is a contact problem.	There are arc marks.	B
   The terminals are not connected securely and there is a contact problem.	There are no arc marks.	C
   The terminals are connected securely and there are no contact problems.	There are arc marks.	B

6. Connect the frame wire to the inverter with converter assembly.
7. Install the upper inverter cover sub-assembly to the inverter with converter assembly.

B → REPLACE MALFUNCTIONING PARTS 

C → CONNECT SECURELY 

A: Go to next step 

1. Visually check the connection of the service plug grip to the electric vehicle battery assembly. Remove the service plug grip and check for contamination.

   OK

   Dirt or foreign objects have not entered the connection, and there is no evidence of contamination.

NG → See step   27 

OK: Go to next step 

1. Measure the resistance according to the value(s) in the table below.
   Fig 3: Measuring Resistance Of Service Plug Grip Terminals

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A - A B - B	Always	Below 1 Ω

   TEXT IN ILLUSTRATION
   
   

   *1	Service Plug Grip

2. Using a megohmmeter set to 500 V, measure the insulation 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
   A - B	Always	10 MΩ or higher

NG → See step   27 

OK: Go to next step 

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

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

2. Disconnect the frame wire from the electric vehicle battery assembly.
   Fig 4: Identifying Frame Wire Connectors

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   TEXT IN ILLUSTRATION
   
   

   *a	Frame Wire Connection Condition (Electric Vehicle Battery Assembly)

3. Remove the upper inverter cover sub-assembly from the inverter with converter assembly.
   Fig 5: Identifying Upper Inverter Cover Sub-Assembly Bolts

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
4. Disconnect the frame wire from the inverter with converter assembly.
   Fig 6: Identifying Frame Wire To Inverter With Converter Assembly Connector

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
5. Measure the resistance according to the value(s) in the table below.
   Fig 7: Measuring Resistance Of Frame Wire (Inverter with Converter Assembly Side) & (Electric Vehicle Battery Assembly Side)

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   TEXT IN ILLUSTRATION
   
   

   *1	Frame Wire (Inverter with Converter Assembly Side)	*2	Shield Ground
   *3	Frame Wire (Electric Vehicle Battery Assembly Side)	-	-

   Standard Resistance

   Tester Connection	Switch Condition	Specified Condition
   bH1-1 (CBI) - H1-2 (CBI) (Positive terminal)	Power switch off	Below 1 Ω
   bH2-1 (CEI) - H1-1 (CEI) (Negative terminal)	Power switch off	Below 1 Ω

6. Using a megohmmeter set to 500 V, measure the insulation 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.
   • Wrap insulating tape around the terminal of the frame wire on the inverter with converter assembly side to prevent it from contacting the body ground.

   Standard Resistance

   Tester Connection	Switch Condition	Specified Condition
   bH1-1 (CBI) - Body ground and shielded ground	Power switch off	10 MΩ or higher
   bH2-1 (CEI) - Body ground and shielded ground	Power switch off	10 MΩ or higher
   bH1-1 (CBI) - bH2-1 (CEI)	Power switch off	10 MΩ or higher

7. Connect the frame wire to the electric vehicle battery assembly.
8. Connect the frame wire to the inverter with converter assembly.
9. Install the upper inverter cover sub-assembly to the inverter with converter assembly.

NG → See step   28 

OK: Go to next step 

NG → See step   19 

OK: Go to next step 

NG → REPAIR OR REPLACE POWER SOURCE CIRCUIT 

OK: Go to next step 

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

NG → See step   24 

OK: Go to next step 

NG → CONNECT SECURELY 

OK → See step   31 

NG → CONNECT SECURELY 

OK: Go to next step 

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK → See step   26 

NG → See step   21 

OK: Go to next step 

Refer to COMPONENTS

NEXT → REPLACE FUSE (PCU) 

NEXT → REPLACE FUSE (PCU) 

B → REPLACE MALFUNCTIONING PARTS 

C → CONNECT SECURELY 

A: Go to next step 

NG → See step   30 

OK → See step   26 

1. Even though it has been determined that the power management control ECU needs to be replaced, make sure to inspect the voltage difference between No. 1 EV battery and No. 2 EV battery before replacing it.

NEXT → See step   32