Lexus ES: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature) (P012800,P012807)

Lexus ES (XZ10) Service Manual / Engine & Hybrid System / A25a-fxs (engine Control) / Sfi System / 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.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	MIL	Memory	Note
P012800	Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)	All of the following conditions are met for 5 seconds or more (2 trip detection logic): The engine is started cold and then warmed up. When the estimated engine coolant temperature is 75°C (167°F) or higher, the actual engine coolant temperature is less than 75°C (167°F).	Water inlet with thermostat sub-assembly (thermostat) Cooling system Engine coolant temperature sensor No. 2 engine coolant temperature sensor ECM	Comes on	DTC stored	SAE Code: P0128
P012807	Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature) Mechanical Failure	All of the following conditions are met for 30 seconds or more (2 trip detection logic): Water inlet housing with water pump sub-assembly is operating, The engine coolant temperature is less than 75°C (167°F). The difference between the rate of change of the engine coolant temperature sensor and No. 2 engine coolant temperature sensor is within the threshold. The difference between the temperature detected by the engine coolant temperature sensor and that detected by the No. 2 engine coolant temperature sensor is within the threshold.	Water inlet with thermostat sub-assembly (thermostat) Cooling system Engine coolant temperature sensor No. 2 engine coolant temperature sensor ECM	Comes on	DTC stored	SAE Code: P0128

MONITOR DESCRIPTION

P012800: Judgment by Simulated Engine Coolant Temperature

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.

P012807: Judgment by Engine Coolant Temperature and No. 2 Engine Coolant Temperature Changes

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

Related DTCs	P0128: Coolant thermostat (judgment by simulated engine coolant temperature) P0128: Coolant thermostat (judgment by engine coolant temperature and No. 2 engine coolant temperature changes)
Required Sensors/Components (Main)	Thermostat Engine coolant temperature sensor
Required Sensors/Components (Related)	Intake air temperature sensor No. 2 engine coolant temperature sensor
Frequency of Operation	Once per driving cycle
Duration	80 seconds: Judgment by simulated engine coolant temperature -: Judgment by engine coolant temperature and No. 2 engine coolant temperature changes
MIL Operation	2 driving cycles
Sequence of Operation	None

TYPICAL ENABLING CONDITIONS

All

Monitor runs whenever the following DTCs are not stored

P0010, P1360, P1362, P1364, P1366, P2614 (Motor drive VVT system control module)

P0011 (VVT system - advance)

P0012 (VVT system - retard)

P0013 (Exhaust VVT oil control solenoid)

P0014 (Exhaust VVT system - advance)

P0015 (Exhaust VVT system - retard)

P0016 (VVT system - misalignment)

P0017 (Exhaust VVT system - misalignment)

P0031, P0032, P101D (Air fuel ratio sensor (sensor 1) heater)

P0087, P0088, P0191, P0192, P0193 (Fuel pressure sensor (for high pressure side))

P0101, P0102, P0103 (Mass air flow meter)

P0107, P0108 (Manifold absolute pressure)

P0111, P0112, P0113 (Intake air temperature sensor)

P0116, P0117, P0118 (Engine coolant temperature sensor)

P0121, P0122, P0123, P0222, P0223, P2135 (Throttle position sensor)

P014C, P014D, P015A, P015B, P2195, P2196, P2237, P2238, P2239, P2252, P2253 (Air fuel ratio sensor (sensor 1))

P0171, P0172 (Fuel system)

P0201, P0202, P0203, P0204, P062D, P21CF, P21D0, P21D1, P21D2 (Fuel injector)

P0300 - P0304 (Misfire)

P0335, P0337, P0338 (Crankshaft position sensor)

P0340, P0342, P0343 (Camshaft position sensor)

P0365, P0367, P0368 (Exhaust camshaft position sensor)

P0401 (EGR system (closed))

P0489, P0490 (EGR control circuit)

P059F, P05A0, P05A2, P05A3, P05A4, P05A5, P05B2, P05B3, P05B4, U0284, U1293, (Active grille air shutter)

P107B, P107C, P107D (Fuel pressure sensor (for low pressure side))

P11EA, P11EC, P11ED, P11EE, P11EF, P219A, P219C, P219D, P219E, P219F (Air-fuel ratio imbalance)

P1235 (High pressure fuel pump circuit)

Judgment by Simulated Engine Coolant Temperature

Auxiliary battery voltage	11 V or higher
Either of the following conditions is met	1 or 2
1. All of the following conditions are met	-
Engine coolant temperature at engine start - Intake air temperature at engine start	-15 to 7°C (-27 to 12.6°F)
Engine coolant temperature at engine start	-10 to 56°C (14 to 133°F)
Intake air temperature at engine start	-10 to 56°C (14 to 133°F)
2. All of the following conditions are met	-
Engine coolant temperature at engine start - Intake air temperature at engine start	Higher than 7°C (12.6°F)
Engine coolant temperature at engine start	56°C (133°F) or less
Intake air temperature at engine start	-10°C (14°F) or higher
Accumulated time that vehicle speed is 128 km/h (80 mph) or more	Less than 20 seconds

Judgment by Engine Coolant Temperature and No. 2 Engine Coolant Temperature Changes

Auxiliary battery voltage	11 V or higher
Engine coolant temperature at first engine start	-10°C (14°F) or higher
Target engine coolant flow by engine water pump	1.5 L/min or higher
Engine coolant temperature sensor malfunction (P0117, P0118)	Not detected
No. 2 engine coolant temperature sensor malfunction (P00B3, P00B4)	Not detected

TYPICAL MALFUNCTION THRESHOLDS

Judgment by Simulated Engine Coolant Temperature

Duration that both of the following conditions are met	5 seconds or more
Estimated engine coolant temperature	75°C (167°F) or higher
Engine coolant temperature sensor output	Less than 75°C (167°F)

Judgment by Engine Coolant Temperature and No. 2 Engine Coolant Temperature Changes

Engine coolant temperature change speed	Less than -0.4°C/sec (31.28°F/sec), or higher than 0.15°C/sec (32.27°F/sec)
Engine coolant temperature	Less than 75°C (167°F)
Grade of engine coolant temperature - No. 2 engine coolant temperature	Higher than -0.1°C/sec (-0.18°F/sec), and less than 0.1°C/sec (0.18°F/sec)
Absolute engine coolant temperature - No. 2 engine coolant temperature	Less than 6.6°C (11.8°F)

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

Turn the power switch off and leave the vehicle for several hours.
Connect the Techstream to the DLC3.
Turn the power switch on (IG) [A].
Turn the Techstream on.
Enter the following menus: Powertrain / Engine / Data List / Coolant Temperature and Intake Air Temperature.
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).
Put the engine in Inspection Mode (Maintenance Mode).
Click here
Start the engine.
Set the heater control to MAX HOT with fresh air mode selected and turn the A/C off.
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.
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.
Enter the following menus: Powertrain / Engine / Trouble Codes [C].
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.
Enter the following menus: Powertrain / Engine / Utility / All Readiness.
Input the DTC: P012800, P012807.

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.
Click here

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

Click here
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

1.	CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P012800 OR P012807)

(a) Connect the Techstream to the DLC3.

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

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

(e) Read the DTCs.

Powertrain > Engine > Trouble Codes

Result	Proceed to
DTC P012800 or P012807 is output	A
DTC P012800, P012807 and other DTCs are output	B

HINT:

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

GO TO DTC CHART

2.	CHECK ENGINE COOLING SYSTEM

(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.

REPAIR OR REPLACE ENGINE COOLING SYSTEM

3.	INSPECT WATER INLET WITH THERMOSTAT SUB-ASSEMBLY

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

Click here

REPLACE WATER INLET WITH THERMOSTAT SUB-ASSEMBLY

4.	INSPECT ENGINE COOLANT TEMPERATURE SENSOR

(a) Inspect the engine coolant temperature sensor.

Click here

HINT:

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

Click here

REPLACE ENGINE COOLANT TEMPERATURE SENSOR

5.	INSPECT NO. 2 ENGINE COOLANT TEMPERATURE SENSOR

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

Click here

REPLACE ECM

REPLACE NO. 2 ENGINE COOLANT TEMPERATURE SENSOR

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