Code No. P0C78: Drive battery precharge time long




danger
  • When servicing the high voltage system parts, always shut off the high voltage by removing the service plug (Refer to ).
  • When servicing the high voltage system parts, always wear the protective equipment or armour to measure the high voltage (Refer to ).
caution
  • If there is any problem in the CAN bus lines, an incorrect diagnosis code may be set. Prior to this diagnosis, diagnose the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table ).
  • Whenever ECU is replaced, ensure that the CAN bus lines are normal.

TROUBLE JUDGEMENT


The PHEV-ECU sets diagnosis code No. P0C78 if the condenser is pre-charged improperly when the drive battery system starts.

PROBABLE CAUSES



  • Damaged harness or connector
  • Loose wire(s) or connector(s) or a fault in the high-voltage wiring harness
  • Blown main high-voltage fuse
  • The drive battery fails: The energisation circuit system/high-voltage circuit of the main contactor (P), (N) or the charging contactor fails (loose high-voltage wiring harness wire or bus bar), or the main contactor (P), (N) or the charging contactor itself fails.
  • Malfunction of electric heater <Vehicles with electric heater>
  • Malfunction of A/C control panel (A/C-ECU)
  • Malfunction of A/C compressor
  • Malfunction of on board charger/DC-DC converter
  • Malfunction of pre-charge resistance
  • Malfunction of PDU
  • Malfunction of rear EMCU
  • Malfunction of PHEV-ECU

DIAGNOSIS PROCEDURE


STEP 1. M.U.T.-III data list


Check that the following data list display contents are normal (Front EMCU, rear EMCU and GCU). (Refer to ).
Data list
  • Item15: Condenser voltage
The value stored in the front EMCU corresponds to the value stored in the rear EMCU or the GCU.

Q. Is the check result normal?

Go to Step 2.
Replace the PDU (Refer to ).

STEP 2. M.U.T.-III diagnosis code.


Check whether the PHEV-ECU related diagnosis code is set.

Q. Is the diagnosis code set?

Diagnose the PHEV-ECU (Refer to ). Then go to Step 23.
Go to Step 3.

STEP 3. M.U.T.-III other system diagnosis code



  • Use M.U.T.-III to check whether the A/C control panel (A/C-ECU) related diagnosis code is set or not. (Refer to GROUP 55 <PHEV> - Diagnosis Code Chart (A/C control panel (A/C-ECU)) )
  • Use M.U.T.-III to check whether the A/C compressor related diagnosis code is set. (Refer to GROUP 55 <PHEV> - Diagnosis Code Chart (A/C compressor) .)

Q. Is the diagnosis code set?

Troubleshoot for the relevant diagnosis code. Then go to Step 23.
NO <Vehicles with electric heater> : Go to Step 4.
NO <Vehicles without electric heater> : Go to Step 5.

STEP 4. Check whether the diagnosis code is set again.


danger
  • Carry out the check on the high-voltage circuit while reading carefully the precautions on handling a high-voltage vehicle.
  • Wear the specified protection equipment during the check.
(1)Erase the diagnosis code.
(2)
danger Isolate bare wires of the disconnected high-voltage circuit with a plastic tape.
Disconnect the high-voltage connector at the electric heater.
(3)Turn on the power supply mode of the electric motor switch.
(4)Check if the diagnosis code is set.

Q. Is the diagnosis code set?

Go to Step 5.
Go to Step 13.

STEP 5. Check whether the diagnosis code is set again.


danger
  • Carry out the check on the high-voltage circuit while reading carefully the precautions on handling a high-voltage vehicle.
  • Wear the specified protection equipment during the check.
(1)Erase the diagnosis code.
(2)
danger Isolate bare wires of the disconnected high-voltage circuit with a plastic tape.
Disconnect the high-voltage connector at the on-board charger and DC/DC converter.
(3)Turn on the power supply mode of the electric motor switch.
(4)Check if the diagnosis code is set.

Q. Is the diagnosis code set?

Go to Step 6.
Check the high-voltage fuse in the rear EMCU and replace if necessary (Refer to ). Replace the on-board charger and DC/DC converter (Refer to ). Then go to Step 23.

STEP 6. Check whether the diagnosis code is set again.


danger
  • Carry out the check on the high-voltage circuit while reading carefully the precautions on handling a high-voltage vehicle.
  • Wear the specified protection equipment during the check.
(1)Erase the diagnosis code.
(2)
danger Isolate bare wires of the disconnected high-voltage circuit with a plastic tape.
Disconnect the high-voltage connector at the A/C compressor.
(3)Turn on the power supply mode of the electric motor switch.
(4)Check if the diagnosis code is set.

Q. Is the diagnosis code set?

Go to Step 7.
Check the high-voltage fuse in the PDU and replace if necessary (Refer to ). Replace the A/C compressor (Refer to GROUP 55 - Compressor Assembly ). Then go to Step 23.

STEP 7. Check the high-voltage fuse.


danger
  • Carry out the check on the high-voltage circuit while reading carefully the precautions on handling a high-voltage vehicle.
  • Wear the specified protection equipment during the check.
(1)Check the main high-voltage fuse in the drive battery (Refer to ).
(2)Check the high-voltage fuse for the electric heater (fuse No. 4 in the rear EMCU) (Refer to ). <Vehicles with electric heater>
(3)Check the high-voltage fuse for the on-board charger and DC/DC converter (fuse No. 5 in the rear EMCU) (Refer to ).
(4)Check the high-voltage fuse for the A/C compressor in the PDU (Refer to ).

Q. Is the check result normal?

Go to Step 9.
NO: <Blown main high-voltage fuse> : Go to Step 8.
NO: <Blown high-voltage fuse for the electric heater> : Diagnose the A/C control panel (A/C-ECU). (Refer to GROUP 55 - Troubleshooting ). Then go to Step 23.
NO <Blown high-voltage fuse for the on-board charger and DC/DC converter> : Diagnose the on-board charger and DC/DC converter. (Refer to .) Then go to Step 23.
NO <Blown high-voltage fuse for the A/C compressor> : Diagnose the A/C compressor. (Refer to GROUP 55 - Troubleshooting ). Then go to Step 23.

STEP 8. M.U.T.-III other system diagnosis code


Use M.U.T.-III to check whether the front EMCU/GCU/rear EMCU related diagnosis code is set. (Refer to ).

Q. Is any diagnosis code set?

Troubleshoot for the relevant diagnosis code. Then go to Step 23.
Replace the main high-voltage fuse (Refer to ). Then go to Step 23.

STEP 9. Check the high-voltage wiring harness.


Check whether the high-voltage wiring harness between the drive battery and the PDU is secured at the specified torque. (Refer to <PDU> and <Drive battery>).
Tightening torque: 7.0 ± 2.0 N·m

Q. Is the check result normal?

Go to Step 10.
Tighten the high-voltage wiring harness to the specified torque. Then go to Step 23.

STEP 10. Check the high-voltage circuit.


danger
  • Carry out the check on the high-voltage circuit while reading carefully the precautions on handling a high-voltage vehicle.
  • Wear the specified protection equipment during the check.
(1)Remove the each cables [EV charging cable (quick charger P, N line), Drive battery front cable (P, N line), Drive battery rear cable (P, N line)] are from drive battery.
(2)Disconnect the drive battery connector, and then apply a voltage of 12 V to the energisation circuit terminal (CNT+, CNT-, CNTP terminal of the drive battery connector) of the respective contactor (main contactor (P), main contactor (N) or charging contactor) to turn on the respective contactor.

(3)Measure the voltage between the terminals at the drive battery rear cable (P, N line) shown in the illustration.
OK: Battery total voltage

Q. Is the check result normal?

Go to Step 17.

Go to Step 11.

STEP 11. Check the resistance at the coil of the contactor.


Refer to .

Q. Is the check result normal?

Go to Step 12.
Go to Step 19.

STEP 12. Check the signal line for short circuit (PHEV-ECU connector and drive battery connector).



  • Check the wiring harness between PHEV-ECU (CNTP, CNT+, CNT- terminals) connector and the drive battery connector.

Q. Is the check result normal?

Go to Step 17.
Repair the connector or wiring harness. Then go to Step 19.

STEP 13. Check whether the electric heater is stuck on.


Disconnect the high-voltage connect at the electric heater, and then check the continuity between the connector terminals at the electric heater side.
OK: 1 MΩ or more

Q. Is the check result normal?

Go to Step 14.
Check the high-voltage fuse in the rear EMCU and replace if necessary (Refer to ). Replace the electric heater (Refer to GROUP 55 - Heater ). Then go to Step 23.

STEP 14. Check the electric heater drive circuit for short to earth.


Disconnect the electric heater connector, and check the heater drive circuit (HTR1, HTR2 and HTR3 terminals) at the electric heater side for short to earth.

Q. Is the check result normal?

Go to Step 15.
Replace the electric heater (Refer to GROUP 55 - Heater ). Then go to Step 23.

STEP 15. Check the electric heater drive circuit for short to earth.


Disconnect the electric heater connector, and check the heater drive circuit (HTR1, HTR2 and HTR3 terminals) at the wiring harness side for short to earth.

Q. Is the check result normal?

The trouble can be an intermittent malfunction (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).
Go to Step 16.

STEP 16. Check the electric heater drive circuit wiring harness for short to earth.


Disconnect the connectors at the electric heater and the A/C ECU (A/C control panel assembly). Check the heater drive circuit (HTR1, HTR2 and HTR3 terminals) for short to earth.

Q. Is the check result normal?

Replace the A/C control panel (A/C-ECU) (Refer to GROUP 55 - Heater Control Unit ). Then go to Step 23.
Repair the connector or wiring harness. Then go to Step 23.

STEP 17. Resistor check


(1)Check whether the terminals are loose.
(2)Check the resistance in the resistor.

Q. Is the check result normal?

Go to Step 18.
Install the resistor properly or replace the resistor. Then go to Step 23.

STEP 18. Check the bus bar for looseness.


Check whether the bus bar in the drive battery and the high-voltage wiring harness are installed properly.

Q. Is the check result normal?

Go to Step 20.
Install the bus bar in the drive battery and the high-voltage wiring harness properly. Then go to Step 23.

STEP 19. Contactor check


Check the contactors.

Q. Is the check result normal?

Repair the wiring harness and the connectors in the drive battery. Then go to Step 23.
Replace the faulty connector(s). Then go to Step 23.

STEP 20. Check whether the diagnosis code is set again.


Recheck if the diagnosis code is set.
(1)Erase the diagnosis code.
(2)Turn on the power supply mode of the electric motor switch.
(3)Check if the diagnosis code is set.

Q. Is the diagnosis code set?

Replace the rear EMCU (Refer to ). Then go to Step 21.
The trouble can be an intermittent malfunction (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).

STEP 21. Check whether the diagnosis code is set again.


Recheck if the diagnosis code is set.
(1)Erase the diagnosis code.
(2)Turn on the power supply mode of the electric motor switch.
(3)Check if the diagnosis code is set.

Q. Is the diagnosis code set?

Replace the PDU (Refer to ). Then go to Step 22 .
The procedure is complete.

STEP 22. Check whether the diagnosis code is set again.


Recheck if the diagnosis code is set.
(1)Erase the diagnosis code.
(2)Turn on the power supply mode of the electric motor switch.
(3)Check if the diagnosis code is set.

Q. Is the diagnosis code set?

Replace the drive battery (Refer to ). Then go to Step 23.
The procedure is complete.

STEP 23. Check whether the diagnosis code is set again.


Recheck if the diagnosis code is set.
(1)Erase the diagnosis code.
(2)Turn on the power supply mode of the electric motor switch.
(3)Check if the diagnosis code is set.

Q. Is the diagnosis code set?

Return to Step 1.
The procedure is complete.




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