HYBRID CONTROL SYSTEM, Diagnostic DTC:P0A78-121

DTC Code DTC Name
P0A78-121 Drive Motor "A" Inverter Performance

DTC SUMMARY

MALFUNCTION DESCRIPTION

This DTC indicates that an overvoltage in the inverter has occurred. The cause of this malfunction may be one of the following:

Area Main Malfunction Description Step
Inverter low-voltage circuit The connectors are not connected properly 3
Resolver Open or short circuit in the motor resolver or generator resolver circuit 4, 5
Motor or generator

  • Open or short circuit in the motor or generator coils

  • An internal motor or generator malfunction (iron particles or damage from foreign objects)

 6, 7
HV battery system High voltage line circuit malfunction 8
Inverter

  • Inverter internal circuit malfunction

  • Malfunction in ECU that controls the inverter

  • Malfunction in the sensors for inverter control (current sensor, voltage sensors (VH, VL), etc.)

 9

DESCRIPTION

For a description of the inverter Click here.

If an overvoltage occurs in the motor inverter or generator inverter, the MG ECU detects it and transmits this information to the power management control ECU.

Tech Tips

The term "drive motor A" indicates motor (MG2).

DTC No. INF Code DTC Detection Condition Trouble Area
P0A78 121

Motor inverter overvoltage signal detected (overvoltage due to system malfunction):

Overvoltage is detected after boosting.

A malfunction is detected in any of the motor components (motor inverter, motor, MG ECU, etc.).*

(1 trip detection logic)

  • Hybrid battery junction block assembly

  • Inverter with converter assembly

  • Service plug grip (EV battery fuse)

  • No. 4 floor wire

  • Hybrid vehicle transaxle assembly

  • Generator cable

  • Motor cable

  • Power management control ECU

  • INV fuse

  • Wire harness or connector

Related Data List
DTC No. Data List
P0A78-121 VH-Voltage after Boosting

MONITOR DESCRIPTION

If the motor inverter detects overvoltage, it will transmit an overvoltage signal to the MG ECU. Upon receiving this signal, the power management control ECU will illuminate the MIL and set a DTC.

MONITOR STRATEGY

Related DTCs P0A78 (INF 121): OVH detection (Over voltage malfunction)
Required sensors / components Motor inverter
Frequency of operation Continuous
Duration TMC's intellectual property
MIL operation 1 driving cycle
Sequence of operation None

TYPICAL ENABLING CONDITIONS

The monitor will run whenever the following DTCs are not present TMC's intellectual property
Other conditions belong to TMC's intellectual property -

TYPICAL MALFUNCTION THRESHOLDS

TMC's intellectual property -

COMPONENT OPERATING RANGE

Power management control ECU DTC P0A78 (INF 121) is not detected

CONFIRMATION DRIVING PATTERN

A01I36OE01

  1. Connect the Techstream to the DLC3.

  2. Turn the power switch on (IG) and turn the Techstream on.

  3. Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure).

  4. Turn the power switch off and wait for 30 seconds or more.

  5. Turn the power switch on (IG) and turn the Techstream on.

  6. Turn the power switch on (READY).

  7. With the shift lever in P and engine stopped, depress the accelerator pedal to start the engine. [A]

  8. Enter the following menus: Powertrain / Hybrid Control / Trouble Codes. [B]

  9. Read the current DTCs.

    Tech Tips


    • If a current DTC is output, the system is malfunctioning.

    • If a current DTC is not output and want to confirm permanent DTC, perform the following procedure.

  10. Check that permanent DTCs are cleared.

  11. If the permanent DTCs are not cleared, perform a universal trip, and then check for permanent DTCs again.

WIRING DIAGRAM

Refer to the wiring diagram for DTC P0A1A-200 Click here.

Refer to the wiring diagram for DTC P0AA6-526 Click here.

Refer to the wiring diagram for DTC P0AE6-225 Click here.

Refer to the wiring diagram for DTC P324E-788 Click here.

Refer to the wiring diagram for DTC U0110-159 Click here.

Refer to the wiring diagram for the inverter low-voltage circuit Click here.

Refer to the wiring diagram for the HV battery high-voltage line circuit Click here.

INSPECTION PROCEDURE

CAUTION:


  • Before inspecting the high-voltage system or disconnecting the low voltage connector of the inverter with converter assembly, take safety precautions such as wearing insulated gloves and removing the service plug grip to prevent electrical shocks. After removing the service plug grip, put it in your pocket to prevent other technicians from accidentally reconnecting it while you are working on the high-voltage system.

  • After removing the service plug grip, wait for at least 10 minutes before touching any of the high-voltage connectors or terminals. After waiting for 10 minutes, check the voltage at the terminals in the inspection point in the inverter with converter assembly. The voltage should be 0 V before beginning work Click here.

    Tech Tips

    Waiting for at least 10 minutes is required to discharge the high-voltage capacitor inside the inverter with converter assembly.

Note

After turning the power switch off, waiting time may be required before disconnecting the cable from the negative (-) auxiliary battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) auxiliary battery terminal notices before proceeding with work Click here.

Tech Tips

After the repair, clear the DTCs and perform the following procedure to check that DTCs are not output.


  1. With the engine stopped, the power switch on (READY) and the shift lever in P, depress the accelerator pedal to start the engine.

PROCEDURE


  1. CHECK DTC OUTPUT (HYBRID CONTROL)


    1. Connect the Techstream to the DLC3.

    2. Turn the power switch on (IG).

    3. Enter the following menus: Powertrain / Hybrid Control / Trouble Codes.

    4. Check if DTCs are output.

      Result
      Result Proceed to
      P0A78-121 only is output, or DTCs except the ones in the table below are also output. A
      Any of the following DTCs including pending DTCs are also output. B
      Relevant DTC
      P0A9C-123 Hybrid Battery Temperature Sensor "A" Range / Performance
      P0A9D-123 Hybrid Battery Temperature Sensor "A" Circuit Low
      P0A9E-123 Hybrid Battery Temperature Sensor "A" Circuit High
      P0AC0-123 Hybrid Battery Pack Current Sensor Circuit Range / Performance
      P0AC1-123 Hybrid Battery Pack Current Sensor Circuit Low
      P0AC2-123 Hybrid Battery Pack Current Sensor Circuit High
      P0AC6-123 Hybrid Battery Temperature Sensor "B" Range / Performance
      P0AC7-123 Hybrid Battery Temperature Sensor "B" Circuit Low
      P0AC8-123 Hybrid Battery Temperature Sensor "B" Circuit High
      P0ACB-123 Hybrid Battery Temperature Sensor "C" Range / Performance
      P0ACC-123 Hybrid Battery Temperature Sensor "C" Circuit Low
      P0ACD-123 Hybrid Battery Temperature Sensor "C" Circuit High
      P0AFC-123 Hybrid Battery Pack Sensor Module
      P3011-123, P3012-123, P3013-123, P3014-123, P3015-123, P3016-123, P3017-123, P3018-123, P3019-123, P3020-123, P3021-123, P3022-123, P3023-123, P3024-123, P3025-123, P3026-123, P3027-123 Battery Block # Becomes Weak
      P3065-123 Hybrid Battery Temperature Sensor Range / Performance Stuck "A"
      P308A-123 Hybrid Battery Voltage Sensor All Circuits Low

      Tech Tips


      • P0A78-121 may be output as a result of the malfunction indicated by the DTCs above.

    5. Turn the power switch off.


    B

    GO TO DTC CHART (HYBRID BATTERY SYSTEM) Click here

    A

  2. CHECK DTC OUTPUT (HYBRID CONTROL)


    1. Connect the Techstream to the DLC3.

    2. Turn the power switch on (IG).

    3. Enter the following menus: Powertrain / Hybrid Control / Trouble Codes.

    4. Check if DTCs are output.

      Result
      Result Proceed to
      P0A78-121 only is output, or DTCs except the ones in the table below are also output. A
      Any of the following DTCs including pending DTCs are also output. B
      Malfunction Content Relevant DTC
      Microcomputer malfunction P0A1A (all INF codes)*1 Generator Control Module
      P0A1B-168, 192, 193, 198, 661, 786, 794, 795, 796 Drive Motor "A" Control Module
      P0A1D (all INF codes)*1 Hybrid Powertrain Control Module
      Power source circuit malfunction P0A1B-163, 164, 511, 512 Drive Motor "A" Control Module
      Sensor and actuator circuit malfunction 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
      P0A4B-253 Generator Position Sensor Circuit
      P0A4C-513 Generator Position Sensor Circuit Range / Performance
      P0A4D-255 Generator 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
      P0A72 (all INF codes)*1 Generator Phase V Current
      P0A75 (all INF codes)*1 Generator Phase W Current
      P0A93-346 Inverter Cooling System Performance
      P0C73-776 Motor Electronics Coolant Pump "A" Control Performance
      P314A-828 Inverter Coolant Pump Speed Signal
      System malfunction P0ADB-227 Hybrid Battery Positive Contactor Control Circuit Low
      P0ADC-226 Hybrid Battery Positive Contactor Control Circuit High
      P0ADF-229 Hybrid Battery Negative Contactor Control Circuit Low
      P0AE0-228 Hybrid Battery Negative Contactor Control Circuit High
      P3004-803 High Voltage Power Resource
      P0A78-113, 128, 266, 267, 279, 284, 286, 287, 306, 503, 504, 505, 506, 565, 586, 806, 807, 808 Drive Motor "A" Inverter Performance
      P0A7A-122, 130, 322, 324, 325, 344, 517, 518, 809, 810, 811 Generator Inverter Performance
      P0A90-509 Drive Motor "A" Performance
      P0A92-521 Hybrid Generator Performance
      P0A94-172, 442, 547, 548, 549, 553, 554, 555, 556, 557, 585, 587, 589, 590 DC / DC Converter Performance
      P0C76-523 Hybrid Battery System Discharge Time Too Long

      Tech Tips


      • *1: If any INF codes are output for this DTC, refer to the corresponding diagnostic procedure.

      • P0A78-121 may be output as a result of the malfunction 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.)

    5. Turn the power switch off.


    B

    GO TO DTC CHART (HYBRID CONTROL SYSTEM) Click here

    A

  3. CHECK CONNECTOR CONNECTION CONDITION (INVERTER WITH CONVERTER ASSEMBLY CONNECTOR)

    CAUTION:

    Be sure to wear insulated gloves.


    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 manual because this may cause a malfunction.

    2. Check the connection condition of the low voltage connector of the inverter with converter assembly and the contact pressure of each terminal. Check the terminals for deformation, and check the connector for water ingress and foreign matter Click here.

      Note

      Before disconnecting the connector, confirm that it is properly connected by checking that the locking claws are engaged and that the connector does not pull out.

      A01I3MYE01
      OK
      - The connector is connected securely.
      - The terminals are not deformed and are connected securely.
      - No water or foreign matter in the connector.
      Result
      Result Proceed to
      OK A
      NG (The connector is not connected securely.) B
      NG (The terminals are not making secure contact or are deformed, or water or foreign matter exists in the connector.) C

      Tech Tips

      When connecting the connector, insert it with the locking lever in the raised position. Rotate the lever downward and make sure that the connector is pulled into its socket. When the locking lever is in its fully closed position, a click will be heard as its locking claws engage. After the click is heard, pull up on the connector to confirm that it is properly connected.


    B

    CONNECT SECURELY

    C

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    A

  4. CHECK GENERATOR RESOLVER CIRCUIT

    Click here


    NEXT

  5. CHECK MOTOR RESOLVER CIRCUIT

    Click here


    NEXT

  6. CHECK GENERATOR HIGH-VOLTAGE CIRCUIT

    Click here


    NEXT

  7. CHECK MOTOR HIGH-VOLTAGE CIRCUIT

    Click here


    NEXT

  8. CHECK HV BATTERY HIGH-VOLTAGE LINE CIRCUIT

    Click here


    NEXT

  9. CHECK INVERTER LOW-VOLTAGE CIRCUIT

    Click here

    Tech Tips

    If the "Inverter Low-voltage Circuit" inspection results are normal, perform the next step.


    NEXT

    REPLACE INVERTER WITH CONVERTER ASSEMBLY Click here