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DTC P0C78: Hybrid BATT. 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 armor to measure the high voltage (Refer to ).
cautionBefore replacing the ECU, ensure that the communication circuit is normal.
 
 
DESCRIPTIONS OF MONITOR METHODS
  • The difference between main drive lithium-ion battery total voltage and inverter voltage is monitored to confirm front electric motor control unit (FEMCU) or rear electric motor control unit (REMCU) capacitor charge status.
  • Front electric motor control unit (FEMCU) or rear electric motor control unit (REMCU) capacitor charge status is judged under the following conditions.
    • Before charge: Main contactor (P) control circuit active command off.
    • Before charge: Main contactor (N) control circuit active command on.
    • Before charge: Charging contactor control circuit active command off.
    • Charging: Main contactor (P) control circuit active command off.
    • Charging: Main contactor (N) control circuit active command on.
    • Charge: Charging contactor control circuit active command on.
 
 
MONITOR EXECUTION
  • Continuous
 
 
MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)
Other Monitor (There is no temporary DTC stored in memory for the item monitored below)
  • EV-CAN monitor
  • Front electric motor control unit (FEMCU) current monitor
  • Front electric motor control unit (FEMCU) coil temperature monitor
  • Front electric motor control unit (FEMCU) IGBT temperature monitor
  • Front electric motor control unit (FEMCU) capacitor temperature monitor
  • Front electric motor control unit (FEMCU) control module temperature monitor
  • Front electric motor control unit (FEMCU) 3 phase circuit monitor
  • Rear electric motor control unit (REMCU) current monitor
  • Rear electric motor control unit (REMCU) coil temperature monitor
  • Rear electric motor control unit (REMCU) IGBT temperature monitor
  • Rear electric motor control unit (REMCU) capacitor temperature monitor
  • Rear electric motor control unit (REMCU) control module temperature monitor
  • Rear electric motor control unit (REMCU) 3 phase circuit monitor
  • Front electric motor control unit (FEMCU) inverter voltage monitor
  • Rear electric motor control unit (REMCU) inverter voltage monitor
  • Front electric motor control unit (FEMCU) Control module circuit monitor
  • Rear electric motor control unit (REMCU) control module circuit monitor
Sensor (The sensor below is determined to be normal)
  • Front electric motor control unit (FEMCU) current sensor
  • Front electric motor control unit (FEMCU) coil temperature sensor
  • Front electric motor control unit (FEMCU) position sensor
  • Front electric motor control unit (FEMCU) IGBT temperature sensor
  • Front electric motor control unit (FEMCU) capacitor temperature sensor
  • Front electric motor control unit (FEMCU) control module temperature sensor
  • Rear electric motor control unit (REMCU) current sensor
  • Rear electric motor control unit (REMCU) coil temperature sensor
  • Rear electric motor control unit (REMCU) position sensor
  • Rear electric motor control unit (REMCU) IGBT temperature sensor
  • Rear electric motor control unit (REMCU) capacitor temperature sensor
  • Rear electric motor control unit (REMCU) control module temperature sensor
  • Front electric motor control unit (FEMCU) inverter voltage sensor
  • Rear electric motor control unit (REMCU) inverter voltage sensor
 
 
DTC SET CONDITIONS
Logic Flow Chart
Check Conditions
  • The charging contactor activation command on.
  • The main contactor (P) activation command off.
  • The main contactor (N) activation command on.
  • Time after above conditions satisfy is 1 second.
Judgment Criterion
  • Before the start of charging, the difference between the value of the main drive lithium-ion battery voltage and the value of the front electric motor control unit (FEMCU) voltage is 70 volts or less for immediately.
  • The difference between the value of the main drive lithium-ion battery voltage and the value of the front electric motor control unit (FEMCU) voltage is 12 volts or more for immediately.
and
  • Before the start of charging, the difference between the value of the main drive lithium-ion battery voltage and the value of the rear electric motor control unit (REMCU) voltage is 70 volts or less for immediately.
  • The difference between the value of the main drive lithium-ion battery voltage and the value of the rear electric motor control unit (REMCU) voltage is 12 volts or more for immediately.
 
 
OBD-II DRIVE CYCLE PATTERN
  • Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 3 .
 
 
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 main drive lithium-ion battery fails: The energization 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 the electric heater.
  • Malfunction of the AC inverter <Vehicles with AC power supply>
  • Malfunction of the A/C control panel (A/C-ECU).
  • Malfunction of the A/C compressor.
  • Malfunction of the on board charger/DC-DC converter.
  • Malfunction of the pre-charge resistance.
  • Malfunction of the power drive unit.
  • Malfunction of the REMCU.
  • Malfunction of the PHEV-ECU.
 
 
DIAGNOSIS
Required Special Tools
  • MB991223: Wiring harness set
  • MB992006: Extra fine probe
STEP 1. Using scan tool (M.U.T.-IIISE), check whether the other DTC is set.
Check if DTC P10C5 is set in the PHEV-ECU.
Is the DTC set?
Go to Step 2.
Go to Step 3.
 
STEP 2. Check the wiring harness for open circuit (EV control relay and PHEV-ECU connector).
Check the wiring harness between EV control relay and the PHEV-ECU connector (terminal CNTB).
Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).
Repair the wiring harness or connector. Then go to Step 20.
 
STEP 3. Using scan tool (M.U.T.-IIISE), check whether the other DTC is set.
Check whether the FEMCU, GCU, REMCU and on board charger/DC-DC converter related DTC is set or not.
Is the DTC set?
Troubleshoot for the relevant DTC. Then go to Step 20.
Go to Step 4.
 
STEP 4. Using scan tool (M.U.T.-IIISE), check whether the other DTC is set.
Check whether DTC is set in the A/C-ECU, A/C compressor assembly and electric heater-ECU (Refer to GROUP 55 - Diagnostic Trouble Code Chart <A/C-ECU>, <A/C compressor assembly>, <electric heater-ECU>).
Is the DTC set?
Troubleshoot for the relevant DTC. Then go to Step 20.
Go to Step 5.
 
STEP 5. Using scan tool (M.U.T.-IIISE), check whether the DTC 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 DTC.
(2)
dangerIsolate bare wires of the disconnected high-voltage circuit with a plastic tape.
Disconnect the high-voltage connector at the electric heater.
(3) Turn off the power supply mode of the electric motor switch.
(4) Depress the brake pedal, and turn on the power supply mode of the electric motor switch (READY operation)*.
note*: When a DTC is set, you cannot make the READY (ready to drive) indicator illuminate by making the READY operation.
(5) Check the DTC.
Is the DTC set?
Go to Step 6.
The electric heater is defective. Go to Step 15.
 
STEP 6. Using scan tool (M.U.T.-IIISE), check whether the DTC 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 DTC.
(2)
dangerIsolate bare wires of the disconnected high-voltage circuit with a plastic tape.
Disconnect the high-voltage connector at the AC inverter <Vehicles with AC power supply>.
(3) Turn off the power supply mode of the electric motor switch.
(4) Depress the brake pedal, and turn on the power supply mode of the electric motor switch (READY operation)*.
note*: When a DTC is set, you cannot make the READY (ready to drive) indicator illuminate by making the READY operation.
(5) Check the DTC.
Is the DTC set?
Go to Step 7.
Replace the AC inverter (Refer to GROUP 54A - AC inverter ). Then go to Step 20.
 
STEP 7. Using scan tool (M.U.T.-IIISE), check whether the DTC 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 DTC.
(2)
dangerIsolate 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 off the power supply mode of the electric motor switch.
(4) Depress the brake pedal, and turn on the power supply mode of the electric motor switch (READY operation)*.
note*: When a DTC is set, you cannot make the READY (ready to drive) indicator illuminate by making the READY operation.
(5) Check the DTC.
Is the DTC set?
Go to Step 8.
Replace the on board charger/DC-DC converter (Refer to ). Then go to Step 20.
 
STEP 8. Using scan tool (M.U.T.-IIISE), check whether the DTC 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 DTC.
(2)
dangerIsolate bare wires of the disconnected high-voltage circuit with a plastic tape.
Disconnect the high-voltage connector at the A/C compressor.
(3) Turn off the power supply mode of the electric motor switch.
(4) Depress the brake pedal, and turn on the power supply mode of the electric motor switch (READY operation)*.
note*: When a DTC is set, you cannot make the READY (ready to drive) indicator illuminate by making the READY operation.
(5) Check the DTC.
Is the DTC set?
Go to Step 9.
Replace the A/C compressor (Refer to GROUP 55 - Compressor Assembly ). Then go to Step 20.
 
STEP 9. 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.
  • Isolate bare wires of the disconnected high-voltage circuit with a plastic tape.
(1) Check the high-voltage fuse No.1 (Normal Charging: 350 A) (integrated with the main drive lithium-ion battery) (Refer to ).
(2) Check the high voltage fuse No.5 [For electric heater (Integrated with the REMCU)] (Refer to ). <Vehicles with electric heater>
(3) Check the high voltage fuse No.4 [For on-board charger/DC-DC converter (Integrated with the REMCU)] (Refer to ).
(4) Check the high voltage fuse No.6 [For AC Inverter (Integrated with junction box)] (Refer to GROUP 54A - AC power supply, On-vehicles service ). <Vehicles with AC power supply>
(5) Check the high voltage fuse No.3 [For A/C compressor (Integrated with power drive unit)] (Refer to ).
Is the check result normal?
Go to Step 10.
: Replace the high-voltage fuse No.1 (Normal Charging: 350 A) (integrated with the main drive lithium-ion battery) (Refer to ). Then go to Step 20.
: Replace the high voltage fuse No.5 [For electric heater (Integrated with the REMCU)] (Refer to ). Then go to Step 20.
: Replace the high voltage fuse No.4 [For on-board charger/DC-DC converter (Integrated with the REMCU)] (Refer to ). Then go to Step 20.
: Replace the high voltage fuse No.6 [For AC Inverter (Integrated with junction box)] (Refer to ). Then go to Step 20.
: Replace the high voltage fuse No.3 [For A/C compressor (Integrated with power drive unit)] (Refer to ). Then go to Step 20 .
 
STEP 10. Check the high-voltage wiring harness.
Check whether the high-voltage wiring harness wires between the main drive lithium-ion battery and the power drive unit as well as between the main drive lithium-ion battery and the FEMCU are secured at the specified torque. (Refer to <Power drive unit>, <Main drive lithium-ion battery>).
Tightening torque: 7.0 ± 2.0 N·m (62 ± 17 in-lb)
Is the check result normal?
Go to Step 11.
Tighten the high-voltage wiring harness to the specified torque. Then go to Step 20.
 
STEP 11. Check the high-voltage wiring harness.
Check whether the high-voltage wiring harness wires between the main drive lithium-ion battery and the power drive unit as well as between the main drive lithium-ion battery and the REMCU are secured at the specified torque (Refer to <Power drive unit>, <Main drive lithium-ion battery> and <REMCU>).
Tightening torque: 7.0 ± 2.0 N·m (62 ± 17 in-lb)
Is the check result normal?
Go to Step 12.
Tighten the high-voltage wiring harness to the specified torque. Then go to Step 20.
 
STEP 12. 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 service plug (Refer to ).
(2) Apply a voltage of 12 volts to the CNT- terminal to turn on the charging contactor.
(3) Connect a high-voltage compatible multimeter between the main drive lithium-ion battery high-voltage terminal (REMCU) and the main drive lithium-ion battery service plug rear terminal.
OK: Approximately 100 - 164 volts

(4) Apply a voltage of 12 volts to the CNTP terminal to turn on the charging contactor.
(5) Connect a high-voltage compatible multimeter between the main drive lithium-ion battery high-voltage terminal (REMCU) and the main drive lithium-ion battery service plug front terminal.
OK: Approximately 100 - 164 volts

(6) Apply a voltage of 12 volts to the CNT+ terminal to turn on the charging contactor.
(7) Connect a high-voltage compatible multimeter between the main drive lithium-ion battery high-voltage terminal (REMCU) and the main drive lithium-ion battery service plug front terminal.
OK: Approximately 100 - 164 volts
Is the check result normal?
Go to Step 14.
: Go to Step 13.
: Go to Step 16.
 
STEP 13. Check the main drive lithium-ion battery main contactor (P) and (N) <On-vehicles check>.
Check resistance of main contactor (P) and (N) coil with harness connector (Refer to ).
Is the check result normal?
Replace the main drive lithium-ion battery assembly (Refer to ). Then go to Step 20.
Go to Step 17.
 
STEP 14. Check the signal line for short to ground circuit (PHEV-ECU connector and main drive lithium-ion battery connector).
Check the wiring harness between PHEV-ECU connector (terminals CNT-) and the main drive lithium-ion battery connector.
Is the check result normal?
Go to Step 19.
Repair the connector or wiring harness. Then go to Step 20.
 
STEP 15. Check whether the electric heater is stuck on.
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 service plug (Refer to ).
(2) Disconnect the electric heater connector (high voltage) and measure at the equipment side.
(3) Measure the resistance between electric heater connector (high voltage) (terminal No.1 and No.2).
OK: No continuity (Reference value: 1 MΩ or more)
Is the check result normal?
Go to Step 16.
Replace the electric heater (Refer to GROUP 55 - Heater ). Then go to Step 20.
 
STEP 16. Resistor check.
(1) Check whether the terminals are loose.
(2) Check the resistance in the resistor.
Is the check result normal?
The procedure is complete.
Replace the main drive lithium-ion battery assembly (Refer to ). Then go to Step 20.
 
STEP 17. Contactor check.
Check the contactors (Refer to ).
Is the check result normal?
Repair the wiring harness and the connectors in the main drive lithium-ion battery. Then go to Step 18.
Replace the faulty connector(s). Then go to Step 20.
 
STEP 18. Test the OBD-II drive cycle.
(1) Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 3 .
(2) Check the DTC.
Is the DTC set?
Replace the PHEV-ECU (Refer to ). Then go to Step 19.
The trouble can be an intermittent malfunction (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).
 
STEP 19. Test the OBD-II drive cycle.
(1) Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 3 .
(2) Check the DTC.
Is the DTC set?
Replace the power drive unit (Refer to GROUP 54Db - Power Drive Unit Removal and Installation ). Then go to Step 20.
The inspection is complete.
 
STEP 20. Test the OBD-II drive cycle.
(1) Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 3 .
(2) Check the DTC.
Is the DTC set?
Retry the troubleshooting.
The inspection is complete.