Toyota Avalon (XX50) 2019-2022 Service & Repair Manual: Engine Coolant Pump Circuit Short to Battery (P26CA12)

DESCRIPTION

The ECM calculates the necessary cooling amount based on the engine coolant temperature, engine speed and vehicle speed, and controls the water inlet housing with water pump sub-assembly accordingly. The water inlet housing with water pump sub-assembly controls the speed of the water inlet housing with water pump sub-assembly steplessly and optimally based on a duty cycle signal sent by the ECM, which reduces engine warm-up time, improves fuel efficiency and reduces cooling loss.

MONITOR DESCRIPTION

The ECM outputs an operation duty signal (WPO) to steplessly control the speed of the water inlet housing with water pump sub-assembly. The ECM outputs an operation duty signal (WPO) to the water inlet housing with water pump sub-assembly and monitors the actual duty signal (WPO) being output. When the actual operation duty signal (WPO) exceeds a certain value when outputting an operation duty signal (WPO) to the water inlet housing with water pump sub-assembly, the ECM detects a malfunction and stores a DTC.

MONITOR STRATEGY

TYPICAL ENABLING CONDITIONS

TYPICAL MALFUNCTION THRESHOLDS

CONFIRMATION DRIVING PATTERN

HINT:

• After repair has been completed, clear the DTC and then check that the vehicle has returned to normal by performing the following All Readiness check procedure.

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• When clearing the permanent DTCs, refer to the "CLEAR PERMANENT DTC" procedure.

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1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG).
3. Turn the Techstream on.
4. Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure).
5. Turn the power switch off and wait for at least 30 seconds.
6. Turn the power switch on (IG) [A].
7. Turn the Techstream on.
8. Put the engine in Inspection Mode (Maintenance Mode).

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9. Start the engine and maintain the engine speed at 2500 rpm or more for at least 40 seconds [B].
10. Enter the following menus: Powertrain / Engine / Trouble Codes [C].
11. Read the pending DTCs.

    HINT:

    • If a pending DTC is output, the system is malfunctioning.
    • If a pending DTC is not output, perform the following procedure.
12. Enter the following menus: Powertrain / Engine / Utility / All Readiness.
13. Input the DTC: P26CA12.
14. Check the DTC judgment result.

    Techstream Display	Description
    NORMAL	DTC judgment completed System normal
    ABNORMAL	DTC judgment completed System abnormal
    INCOMPLETE	DTC judgment not completed Perform driving pattern after confirming DTC enabling conditions

    HINT:

    • If the judgment result is NORMAL, the system is normal.
    • If the judgment result is ABNORMAL, the system has a malfunction.
    • If the judgment result is INCOMPLETE, perform steps [B] through [C] again.
    • [A] to [C]: Normal judgment procedure.

      The normal judgment procedure is used to complete DTC judgment and also used when clearing permanent DTCs.

    • When clearing the permanent DTCs, do not disconnect the cable from the auxiliary battery terminal or attempt to clear the DTCs during this procedure, as doing so will clear the universal trip and normal judgment histories.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

• Vehicle Control History may be stored in the hybrid vehicle control ECU assembly if the engine is malfunctioning. Certain vehicle condition information is recorded when Vehicle Control History is stored. Reading the vehicle conditions recorded in both the Freeze Frame Data and Vehicle Control History can be useful for troubleshooting.

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  (Select Powertrain in Health Check and then check the time stamp data.)

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• If any "Engine Malfunction" Vehicle Control History item has been stored in the hybrid vehicle control ECU assembly, make sure to clear it. However, as all Vehicle Control History items are cleared simultaneously, if any Vehicle Control History items other than "Engine Malfunction" are stored, make sure to perform any troubleshooting for them before clearing Vehicle Control History.

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HINT:

Read Freeze Frame Data using the Techstream. The ECM records vehicle and driving condition information as Freeze Frame Data the moment a DTC is stored. When troubleshooting, Freeze Frame Data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air fuel ratio was lean or rich, and other data from the time the malfunction occurred.

PROCEDURE

(a) Disconnect the water inlet housing with water pump sub-assembly connector.

(b) Turn the power switch on (IG).

(c) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

NG

GO TO STEP 3

OK

(a) Disconnect the water inlet housing with water pump sub-assembly connector.

(b) Turn the power switch on (IG).

(c) Measure the resistance according to the value(s) in the table below.

Standard:

HINT:

• *: When the connector of the water inlet housing with water pump sub-assembly is disconnected, the ECM will enter fail-safe mode. In this case, duty control of the transistors in the ECM will be performed and resistance fluctuates.
• If the resistance fluctuates while the ECM is in fail-safe mode after the connector of the water inlet housing with water pump sub-assembly is disconnected, it can be determined that the transistor is operating.
• If the transistor does not operate, the ECM may be malfunctioning.
• If the resistance fluctuates after turning the power switch on (IG), it can be determined that the ECM is in fail-safe mode.

OK

REPLACE WATER INLET HOUSING WITH WATER PUMP SUB-ASSEMBLY

NG

REPLACE ECM

(a) Disconnect the water inlet housing with water pump sub-assembly connector.

(b) Disconnect the ECM connector.

(c) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

OK

REPLACE ECM

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR