Lexus RX (RX 350L, RX450h) 2016-2024 Repair Manual: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature) (P012800,P012807)

Lexus RX (RX 350L, RX450h) 2016-2024 Repair Manual / Engine & Hybrid System / 2gr-fks (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, 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): Cold start. The engine is warmed up. The engine coolant temperature is less than 75°C (167°F).	Water inlet with thermostat sub-assembly Engine cooling system 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 3 times (2 trip detection logic): The engine coolant temperature is less than 75°C (167°F). The value of the change in engine coolant temperature is less than the threshold.	Water inlet with thermostat sub-assembly Engine cooling system 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 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.

P012807: Judgment by Engine Coolant Temperature Change at High Vehicle Speed

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

Related DTCs	P0128: Coolant thermostat (judgment by simulated engine coolant temperature) P0128: Coolant thermostat (judgment by engine coolant temperature change at high vehicle speed)
Required Sensors/Components (Main)	Thermostat Engine coolant temperature sensor
Required Sensors/Components (Related)	Intake air temperature sensor (for mass air flow meter sub-assembly) Vehicle speed sensor
Frequency of Operation	Once per driving cycle: Judgment by simulated engine coolant temperature Continuous: Judgment by engine coolant temperature change at high vehicle speed
Duration	423 seconds: Judgment by simulated engine coolant temperature -: Judgment by engine coolant temperature change at high vehicle speed
MIL Operation	2 driving cycles
Sequence of Operation	None

TYPICAL ENABLING CONDITIONS

ALL

Monitor runs whenever the following DTCs are not stored

P0010, P0020 (VVT oil control solenoid bank 1, 2)

P0011, P0021 (VVT system bank 1, 2 - advance)

P0012, P0022 (VVT system bank 1, 2 - retard)

P0013, P0023 (Exhaust VVT oil control solenoid bank 1, 2)

P0014, P0024 (Exhaust VVT system bank 1, 2 - advance)

P0015, P0025 (Exhaust VVT system bank 1, 2 - retard)

P0016, P0018 (VVT system bank 1, 2 - misalignment)

P0017, P0019 (Exhaust VVT system bank 1, 2 - misalignment)

P0031, P0032, P0051, P0052, P101D, P103D (Air fuel ratio sensor heater)

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

P0101, P0102, P0103 (Mass air flow meter)

P0111, P0112, P0113 (Intake air temperature sensor)

P0116, P0117, P0118 (Engine coolant temperature sensor)

P011B (Engine coolant temperature/intake air temperature sensor correlation)

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

P014C, P014D, P014E, P014F, P015A, P015B, P015C, P015D, P2195, P2196, P2197, P2198, P2237, P2238, P2239, P2240, P2241, P2242, P2252, P2253, P2255, P2256 (Air fuel ratio sensor)

P0171, P0172, P0174, P0175 (Fuel system)

P0201, P0202, P0203, P0204, P0205, P0206, P062D, P21CF, P21D0, P21D1, P21D2, P21D3, P21D4 (Fuel injector)

P0300 - P0306 (Misfire)

P0335, P0337, P0338 (Crankshaft position sensor)

P0340, P0342, P0343, P0345, P0347, P0348 (Camshaft position sensor)

P0365, P0367, P0368, P0390, P0392, P0393 (Exhaust camshaft position sensor)

P0500 (Vehicle speed sensor)

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

P11EA, P11EB, P11EC, P11ED, P11EE, P11EF, P11F0, P11F1, P219A, P219B P219C, P219D, P219E, P219F, P21A0, P21A1 (Air-fuel ratio imbalance)

P1235 (High pressure fuel pump circuit)

P0128: Judgment by Simulated Engine Coolant Temperature

Battery voltage	11 V or higher
Either of the following conditions is met	1 or 2
1. All of the following conditions are met	(a), (b) and (c)
(a) Engine coolant temperature at engine start - Intake air temperature (for mass air flow meter sub-assembly) at engine start	-15 to 7°C (-27 to 12.6°F)
(b) Engine coolant temperature at engine start	-10 to 56°C (14 to 133°F)
(c) Intake air temperature (for mass air flow meter sub-assembly) at engine start	-10 to 56°C (14 to 133°F)
2. All of the following conditions are met	(d), (e) and (f)
(d) Engine coolant temperature at engine start - Intake air temperature (for mass air flow meter sub-assembly) at engine start	Higher than 7°C (12.6°F)
(e) Engine coolant temperature at engine start	56°C (133°F) or less
(f) Intake air temperature (for mass air flow meter sub-assembly) at engine start	-10°C (14°F) or higher
Accumulated time at vehicle speed of 128 km/h (80 mph) or more	Less than 20 seconds

P0128: Judgment by Engine Coolant Temperature Change at High Vehicle Speed

During that all of the following conditions are met	15 seconds or more
Battery voltage	11 V or higher
Engine coolant temperature at engine start	-10°C (14°F) or higher
Intake air temperature at engine start	-10°C (14°F) or higher
Engine speed	Less than 4500 rpm
Vehicle speed	65 to 128 km/h (40.625 to 80 mph)

TYPICAL MALFUNCTION THRESHOLDS

P0128: Judgment by Simulated Engine Coolant Temperature

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

P0128: Judgment by Engine Coolant Temperature Change at High Vehicle Speed

Malfunction counter	3 times or more
Malfunction counter is incremented when following conditions are met	A and B
A. Average engine coolant temperature change (vary with current engine coolant temperature, estimated ambient air temperature, intake air mass and vehicle speed)	Less than -0.04°C/sec (-0.072°F/sec)
B. Engine coolant temperature is satisfied throughout this period	Less than 75°C (167°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

Stop the engine and allow it to soak.
Connect the Techstream to the DLC3.
Turn the engine 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).
Set the heater control to MAX HOT with fresh air mode selected and turn the A/C off.
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.
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 or 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 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].

With the engine stopped, leave the vehicle outside overnight [D].
Turn the engine switch on (IG) [E].
Turn the Techstream on.
Enter the following menus: Powertrain / Engine / Data List / Coolant Temperature.
Check that the value of the Data List item Coolant Temperature is 25°C (77°F) or less.
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.
Enter the following menus: Powertrain / Engine / Trouble Codes [G].
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 or P012807.

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

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

(a) Connect the Techstream to the DLC3.

(b) Turn the engine 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 or 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 too 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 ECM

REPLACE ENGINE COOLANT TEMPERATURE SENSOR

Insufficient Coolant Temperature for Closed Loop Fuel Control (P012500)

DESCRIPTION Refer to DTC P011511. Click here DTC No. Detection Item DTC Detection Condition Trouble Area MIL Memory Note P012500 Insufficient Coolant Temperature for Closed Loop ...

O2 Sensor Circuit Bank 1 Sensor 2 Circuit Short to Ground (P013611,...,P015623)

DESCRIPTION In order to obtain a high purification rate of the carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NOx) components in the exhaust gas, a TWC (Three-Way Catalytic Converter) is u ...

Other materials:

Lexus RX (RX 350L, RX450h) 2016-2024 Repair Manual > Mass Air Flow Meter: On-vehicle Inspection
ON-VEHICLE INSPECTION PROCEDURE 1. INSPECT MASS AIR FLOW METER SUB-ASSEMBLY HINT: Perform "Inspection After Repair" after replacing the mass air flow meter sub-assembly. Click here (a) Read the value of Data List item "Mass Air Flow Sensor" using the Techstream. NOTICE: Perform the inspection of ...

Lexus RX (RX 350L, RX450h) 2016-2024 Repair Manual > Wireless Charging System: Wireless Charger Illumination Circuit
DESCRIPTION When the light control switch is turned to the tail or head position, this circuit sends an illumination signal to the mobile wireless charger cradle assembly. WIRING DIAGRAM CAUTION / NOTICE / HINT NOTICE: Inspect the fuses for circuits related to this system before performing the foll ...

Lexus RX (RX 350L, RX450h) 2016-2024 Repair Manual: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature) (P012800,P012807)

Insufficient Coolant Temperature for Closed Loop Fuel Control (P012500)

O2 Sensor Circuit Bank 1 Sensor 2 Circuit Short to Ground (P013611,...,P015623)

Other materials:

Lexus RX (RX 350L, RX450h) 2016-{YEAR} Owners Manual

Lexus RX (RX 350L, RX450h) 2016-{YEAR} Repair Manual