The driving of the water pump is controlled by the EV-ECU. The water pump relay is controlled
by the EV-ECU and supplies the power to the water pump.
DIAGNOSIS CODE SET CONDITIONS
When the water pump speed of 1,000 r/min or
less continues for 0.5 second or longer while the water pump drive command is underway, the
diagnosis code No. P0C73 will be set.
PROBABLE CAUSES
Damaged wiring harness or connector(s)
Malfunction of the water pump relay
Malfunction of the water pump
Incorrect concentration of the coolant
Malfunction of the EV-ECU
DIAGNOSIS PROCEDURE
STEP 1. 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 2.
Adjust so that the concentration of the coolant is within the standard value.
STEP 2. M.U.T.-III actuator test
Conduct the actuator test, and check the water pump relay. (Refer to .)
Erase the stored diagnosis code.
Set the electric motor switch from the "LOCK" (OFF) position to the "ON" position.
Actuator test
Item No. 10 : Water pump power supply relay
OK: The water pump relay operates normally.
Q.
Is the check result normal?
Go to Step 3.
Check the water pump relay. (Refer to GROUP 14 - On-vehicle Service -
Water Pump Relay Continuity Check .)
STEP 3. Measure the voltage at E-10 water pump connector.
(1)Disconnect the E-10 water pump connector, and measure the voltage at the wiring
harness side.
(2)Turn the electric motor switch to the "ON" position.
(3)Measure the voltage between the E-10 water pump connector terminal No. 3 and the
body earth. OK: Battery voltage
Q.
Is the check result normal?
Go to Step 8.
Go to Step 4.
STEP 4. Connector check: A-09X water pump relay, E-10 water pump connector
Q.
Is the check result normal?
Go to Step 5.
Repair the damaged connector. Or, correct or replace the relay box.
STEP 5. Check the wiring harness between A-09X water pump relay (relay
box) connector terminal No. 4 and the fuse (No. 10).
Check the power supply line for open circuit.
Q.
Is the check result normal?
Go to Step 6.
Repair the wiring harness.
STEP 6. Check the wiring harness between A-09X water pump relay (relay
box) connector terminal No. 1 and E-10 water pump connector terminal No. 3.
Check the power supply line for open circuit.
Q.
Is the check result normal?
Go to Step 7.
Repair the wiring harness.
STEP 7. Check the wiring harness between E-10 water pump connector
terminal No. 4 and the body earth.
Check the earth line for open circuit.
Q.
Is the check result normal?
Go to Step 8.
Repair the wiring harness.
STEP 8. Connector check: C-111 EV-ECU connector
Q.
Is the check result normal?
Go to Step 9.
Repair the damaged connector.
STEP 9. Check the wiring harness between C-111 EV-ECU connector terminal
No. 113, 125 and E-10 water pump connector terminal No. 1, 2.
Check the signal lines for open circuit.
Q.
Is the check result normal?
Go to Step 10.
Repair the wiring harness.
STEP 10. 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 ).
Erase the stored diagnosis code.
Set the electric motor switch from the "LOCK" (OFF) position to the "ON" position.
Actuator test
Item No. 3 : Water pump actuate
OK: The water pump operates normally.
Data list
Item No. 205 : Water pump speed
Q.
Is the check result normal?
Go to Step 11.
Replace the water pump. (Refer to GROUP 14 - Water Pump Removal and Installation .)
Then go to Step 11.
STEP 11. 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
12.
The diagnosis is complete.
STEP 12. 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.
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Go to Step 2.
Adjust so that the concentration of the coolant is within the standard value.