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, to monitor the operation of the thermostat.

MONITOR DESCRIPTION

The ECM estimates the engine coolant temperature based on the starting temperature, engine loads, and engine speeds. 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 in the thermostat or the engine cooling system and stores the DTC.

When the vehicle is being driven between 65 and 128 km/h (40.625 and 80 mph) and the monitoring conditions are met, the change in engine coolant temperature is monitored. The amount of change is judged to be normal or abnormal every 15 seconds, in order to monitor the thermostat operation. If the engine coolant temperature changes more than the threshold, the thermostat is judged as normal, but if it changes less than the threshold, the thermostat is judged to be malfunctioning. If an abnormal judgment is made 3 times, the ECM will 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.

  Click here

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

  Click here

1. Stop the engine and allow it to soak.
2. Connect the Techstream to the DLC3.
3. Turn the engine 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. Set the heater control to MAX HOT with fresh air mode selected and turn the A/C off.
8. Start the engine and drive the vehicle at 80 km/h (50 mph) or more for 20 minutes [B].

   CAUTION:

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

9. 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.

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: P012800 or P012807.
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, If the judgment result is INCOMPLETE, perform steps [D] through [G].
15. With the engine stopped, leave the vehicle outside overnight [D].
16. Turn the engine switch on (IG) [E].
17. Turn the Techstream on.
18. Enter the following menus: Powertrain / Engine / Data List / Coolant Temperature.
19. Check that the value of the Data List item Coolant Temperature is 25°C (77°F) or less.
20. Start the engine and drive the vehicle at 90 km/h (56 mph) or more for 20 minutes [F].

    CAUTION:

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

21. Enter the following menus: Powertrain / Engine / Trouble Codes [G].
22. 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.
23. Enter the following menus: Powertrain / Engine / Utility / All Readiness.
24. Input the DTC: P012800 or P012807.
25. Check the DTC judgment result again.

    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.
    • [D] to [G]: 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 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

HINT:

• When the DTC is output, check the engine coolant temperature using the Techstream. Enter the following menus: Powertrain / Engine / Data List / Coolant Temperature. If the Coolant Temperature value 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 those connections) 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 engine 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 too 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.

Click here

HINT:

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

Click here

OK

REPLACE ECM

NG

REPLACE ENGINE COOLANT TEMPERATURE SENSOR