Code No. P0C74: Water pump error (high speed)


WATER PUMP CIRCUIT



OPERATION



DIAGNOSIS CODE SET CONDITIONS



  • When the water pump speed of 5,000 r/min or more continues for 2 seconds or longer while the water pump drive command is underway, the diagnosis code No. P0C74 will be set.

PROBABLE CAUSES



  • Low coolant level
  • Incorrect concentration of the coolant
  • Clogging of the coolant circuit
  • Malfunction of the water pump
  • Malfunction of the EV-ECU

DIAGNOSIS PROCEDURE

STEP 1. Coolant level check
Refer to GROUP 14 - Coolant Level Check ().

Q. Is the check result normal?
Go to Step 2.
Add or replace the coolant. (Refer to GROUP 14 - On-vehicle Service - Coolant Replacement .)

STEP 2. Coolant freeze check
Check the concentration of the coolant for possibility of freezing. (Refer to GROUP 14 - Coolant Concentration Check ().

Q. Is the check result normal?
Go to Step 3.
Adjust so that the concentration of the coolant is within the standard value.

STEP 3. Measure the water pump output waveform at the C-111 EV-ECU connector (using the oscilloscope).
With the C-111 EV-ECU connector connected, connect the oscilloscope probe to the harness of the C-111 EV-ECU connector terminal No.125.
(1)Set the electric motor switch from the "LOCK" (OFF) position to the "ON" position.
(2)Vehicle speed 0 km/h
OK: The pulse wave pattern is not set.

Q. Is the check result normal?
Go to Step 4.
Replace the water pump. (Refer to GROUP 14 - Water Pump Removal and Installation .)

STEP 4. M.U.T.-III actuator test and service data
Conduct the actuator test (refer to ), and check the service data of the water pump (refer to ).

  1. Erase the stored diagnosis code.
  2. Set the electric motor switch from the "LOCK" (OFF) position to the "ON" position.
Actuator test
  • Item No. 3 : Water pump drive
OK: The water pump operates normally.
Data list
  • Item No. 205 : WP rotation

Q. Is the check result normal?
Go to Step 5.
Replace the water pump. (Refer to GROUP 14 - Water Pump Removal and Installation .)

STEP 5. Diagnosis code recheck
Check again if the diagnosis code is set to the EV-ECU.
(1)Erase the stored diagnosis code.
(2)Set the electric motor switch from the "LOCK" (OFF) position to the "ON" position.
(3)Check if the diagnosis code is set.

Q. Is the diagnosis code set?
Replace the EV-ECU. (Refer to .) Then go to Step 6.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction .)

STEP 6. Diagnosis code recheck
Check again if the diagnosis code is set to the EV-ECU.
(1)Erase the stored diagnosis code.
(2)Set the electric motor switch from the "LOCK" (OFF) position to the "ON" position.
(3)Check if the diagnosis code is set.

Q. Is the diagnosis code set?
Return to Step 1.
The diagnosis is complete.