Toyota Avalon (XX50) 2019-2022 Service & Repair Manual: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature) (P012800,P012807)

DESCRIPTION

The ECM uses the engine coolant temperature sensor, installed to the water outlet, and the No. 2 engine coolant temperature sensor, installed to the radiator pipe assembly, to monitor the operation of the thermostat.

MONITOR DESCRIPTION

The ECM estimates the engine coolant temperature based on the starting temperature, engine load, and engine speed. The ECM then compares the estimated temperature with the actual engine coolant temperature. When the estimated engine coolant temperature reaches 75°C (167°F), the ECM checks the actual engine coolant temperature. If the actual engine coolant temperature is less than 75°C (167°F), the ECM interprets this as a malfunction of the thermostat or in the engine cooling system, illuminate the MIL and stores this DTC.

When the engine coolant temperature is less than 75°C (167°F) and the water inlet housing with water pump sub-assembly is operating, if the rate of change and detected temperature of the engine coolant temperature sensor and No. 2 engine coolant temperature sensor differ by less than 0.1°C/sec. and 6.6°C respectively for a certain amount of time, the ECM will determine that the thermostat is stuck open, illuminate the MIL and store 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. Turn the power switch off and leave the vehicle for several hours.
2. Connect the Techstream to the DLC3.
3. Turn the power switch on (IG) [A].
4. Turn the Techstream on.
5. Enter the following menus: Powertrain / Engine / Data List / Coolant Temperature and Intake Air Temperature.
6. Check that the value of the Data List item Coolant Temperature is 56°C (133°F) or less and the value of the Data List item Intake Air Temperature is between 0 and 35°C (32 and 95°F).
7. Put the engine in Inspection Mode (Maintenance Mode).

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8. Start the engine.
9. Set the heater control to MAX HOT with fresh air mode selected and turn the A/C off.
10. With the engine running, drive the vehicle at 80 km/h (50 mph) for 15 minutes [B].

    CAUTION:

    When performing the confirmation driving pattern, obey all speed limits and traffic laws.

    HINT:

    If the engine stops, further depress the accelerator pedal to restart the engine.

11. After the value of the Data List item Coolant Temperature stabilizes, check that it is 75°C (167°F) or higher.

    HINT:

    If the value of the Data List item Coolant Temperature is less than 75°C (167°F) while driving the vehicle at 80 km/h (50 mph), inspect the cooling system and thermostat.

12. Enter the following menus: Powertrain / Engine / Trouble Codes [C].
13. 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.
14. Enter the following menus: Powertrain / Engine / Utility / All Readiness.
15. Input the DTC: P012800, P012807.
16. 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 shows NORMAL, the system is normal.
    • If the judgment result shows ABNORMAL, the system has a malfunction.
    • If the judgment result is INCOMPLETE, let the engine cool down (engine coolant temperature is 56°C (133°F) or less), and then perform steps [A] through [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.

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.

  Click here

HINT:

• When this DTC is output, check the engine coolant temperature using the Techstream. Enter the following menus: Powertrain / Engine / Data List / Coolant Temperature. If the value of Coolant Temperature is lower than the actual engine coolant temperature, the engine coolant temperature sensor circuit may be malfunctioning. In this case, check the wire harnesses and connectors (and their connection condition) between the ECM and the engine coolant temperature sensor first.
• 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) Connect the Techstream to the DLC3.

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

(c) Turn the Techstream on.

(d) Enter the following menus: Powertrain / Engine / Trouble Codes.

(e) Read the DTCs.

HINT:

If any DTCs other than P012800 or P012807 are output, troubleshoot those DTCs first.

B

GO TO DTC CHART

A

(a) Check for defects in the engine cooling system that might cause the system to be excessively cold, such as abnormal cooling fan operation or any modifications.

NG

REPAIR OR REPLACE ENGINE COOLING SYSTEM

OK

(a) Inspect the water inlet with thermostat sub-assembly (thermostat opening temperature).

Click here

NG

REPLACE WATER INLET WITH THERMOSTAT SUB-ASSEMBLY

OK

(a) Inspect the engine coolant temperature sensor.

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HINT:

Perform "Inspection After Repair" after replacing the engine coolant temperature sensor.

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NG

REPLACE ENGINE COOLANT TEMPERATURE SENSOR

OK

(a) Inspect the No. 2 engine coolant temperature sensor.

Click here

OK

REPLACE ECM

NG

REPLACE NO. 2 ENGINE COOLANT TEMPERATURE SENSOR