Code No. P0C73 Abnormal EV cooling system 1




caution
  • If there is any problem in the CAN bus lines, an incorrect diagnosis code may be stored. 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 stores diagnosis code No. P0C73 when the EV cooling system fails.

PROBABLE CAUSES



  • Frozen coolant
  • Damaged harness or connector
  • Malfunction of electric water/oil pump relay
  • Malfunction of electric water pump
  • Malfunction of PHEV-ECU

DIAGNOSIS PROCEDURE


STEP 1. Check whether the diagnosis code is stored.


Check if the diagnosis code No. P1B2B is stored in the PHEV-ECU.

Q. Is the diagnosis code stored?

Carry out troubleshooting for the diagnosis code P1B2B. (Refer to .)
Go to Step 2.

STEP 2. Motor coolant level check


Refer to GROUP 14B - Motor Coolant Level Check .

Q. Is the check result normal?

Go to Step 3.
Adjust the motor coolant level (between the EV radiator condenser tank "FULL" and "LO" lines).

STEP 3. Coolant concentration check


Refer to GROUP 14B - Motor Concentration Check .

Q. Is the check result normal?

Go to Step 4.
Adjust the motor coolant concentration between 30 and 60% (service concentration range).

STEP 4. Measure the output waveform at the WPN wire of the PHEV-ECU connector (using the oscilloscope).


(1)Use the test harness (MB991709) to connect the connector, and then measure at the pick-up wiring harness section.
(2)Measure the pulse at the WPN wire between the PHEV-ECU connector and body earth.

Q. Is the check result normal?

Go to Step 10.
Go to Step 5.

STEP 5. M.U.T.-III actuator test


Conduct the actuator test, and check the electric water/oil pump relay. (Refer to .)

  1. Erase the stored diagnosis code.
  2. Turn on the power supply mode of the electric motor switch.
    note The READY (ready to drive) indicator should not illuminate at a vehicle speed of 0 km/h (vehicle stationary).
Actuator test
  • Item No. 9: Water/oil pump power supply relay
OK: The electric water pump/oil relay works normally.

Q. Is the check result normal?

Go to Step 7.
Go to Step 6.

STEP 6. Water/oil pump relay check


Refer to GROUP 14B - On-vehicle Service, Water/oil pump relay check .

Q. Is the check result normal?

The trouble can be an intermittent malfunction (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).
Replace the damaged water/oil pump relay. Then go to Step 11.

STEP 7. Check the signal line for short circuit (water/oil pump relay connector and PHEV-ECU connector)



  • Check the wiring harness between water/oil pump relay connector and the PHEV-ECU (WPR- terminal) connector.

Q. Is the check result normal?

Go to Step 8.
Repair the wiring harness.

STEP 8. Check the power supply line for open and short circuit (water/oil pump relay connector and electric water pump connector)



  • Check the wiring harness between water/oil pump relay connector terminal No. 3 and the electric water pump connector terminal No. 1.

Q. Is the check result normal?

Go to Step 9.
Repair the wiring harness.

STEP 9. Check the earth line for open and short circuit (electric water pump connector and body earth).



  • Check the wiring harness between electric water pump connector terminal No. 4 and body earth.

Q. Is the check result normal?

Go to Step 10.
Repair the wiring harness.

STEP 10. Check the signal line for open and short circuit (PHEV-ECU connector and electric water pump connector).



  • Check the wiring harness between PHEV-ECU (WP terminal) connector and electric water pump connector.

Q. Is the check result normal?

Replace the electric water pump. (Refer to GROUP 14B - Water Pump Removal and Installation .) Then go to Step 11.
Repair the wiring harness.

STEP 11. Check whether the diagnosis code is stored again.


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

Q. Is the diagnosis code stored?

Replace the PHEV-ECU (Refer to ).
The procedure is complete.