A thermistor built into the sensor changes its resistance value according to the exhaust gas temperature. The lower the exhaust gas temperature, the greater the thermistor resistance value. The higher the exhaust gas temperature, the lower the thermistor resistance value.

The exhaust gas temperature sensor is connected to the ECM. The 5 V power source voltage in the ECM is applied to the exhaust gas temperature sensor from terminals THCI (upstream) and THCO (downstream) via resistor R.

The resistor R and the exhaust gas temperature sensor are connected in series. When the resistance value of the exhaust gas temperature sensor changes in accordance with changes in the exhaust gas temperature, the voltage at terminals THCI (upstream) and THCO (downstream) also changes. Based on these signals, when DPNR catalyst regeneration is needed, the ECM operates the exhaust fuel addition injector to obtain target upstream temperature of the DPNR catalytic converter as mentioned through sensor 1. In addition, the ECM monitors the rate of DPNR catalytic converter temperature increase using sensor 2.

*1: Diesel Particulate-NOx Reduction system.

DTC No.	DTC Detection Condition	Trouble Area
P0544	Sensor 1 output is less than 0.2 V or more than 4.95 V for 3 seconds or more (1 trip detection logic)	Open or short in exhaust gas temperature sensor (upstream) circuit Exhaust gas temperature sensor (upstream) ECM
P0545	Sensor 1 output is less than 0.2 V for 3 seconds or more (1 trip detection logic)
P0546	Sensor 1 output is more than 4.95 V for 3 seconds or more (1 trip detection logic)
P2031	Sensor 2 output is less than 0.2 V or more than 4.95 V for 3 seconds or more (1 trip detection logic)	Open or short in exhaust gas temperature sensor (downstream) circuit Exhaust gas temperature sensor (downstream) ECM
P2032	Sensor 2 output is less than 0.2 V for 3 seconds or more (1 trip detection logic)
P2033	Sensor 2 output is more than 4.95 V for 3 seconds or more (1 trip detection logic)

HINT:

DTC P1386 (Exhaust fuel addition injector malfunction) will be present if there is an open malfunction in an exhaust gas temperature sensor circuit.

Sensor 1 represents a sensor located upstream on the DPNR catalytic converter.

Sensor 2 represents a sensor located downstream on the DPNR catalytic converter.

After confirming DTC P0544, P0545, P0546, P2031, P2032, and P2033, check the upstream and downstream exhaust gas temperature in the "Powertrain / Engine / Initial Exhaust Temp (IN) and Initial Exhaust Temp (OUT)" using the intelligent tester.

Reference:
Condition	Exhaust Gas Temperature	Exhaust Gas Temperature Sensor Condition
Idling after warm-up	Constant at 50 to 700°C (122 to 1,292°F)	Normal
	0°C (32°F)	Short circuit
	1,000°C (1,832°F)	Open circuit

MONITOR DESCRIPTION

The ECM constantly monitors the output voltages from the sensors in order to detect problems with the sensors. When the sensor output voltage deviates from the normal operating range (between 0.2 V and 4.95 V) for more than 3 seconds after the engine is warmed up, the ECM interprets this as a malfunction of the sensor circuit, and illuminates the MIL.

WIRING DIAGRAM

Dtc P0544 Exhaust Gas Temperature Sensor Circuit (Bank 1 Sensor 1). 2AD-FHV ENGINE CONTROL SYSTEM. Lexus IS250 IS220d GSE20 ALE20

INSPECTION PROCEDURE

NOTICE:

After replacing the ECM, the new ECM needs registration and initialization .

1.READ VALUE OF EXHAUST GAS TEMPERATURE SENSOR

Connect the intelligent tester to the DLC3.

Turn the engine switch ON (IG) and turn the intelligent tester ON.

Enter the following menus: "Powertrain / Engine / Initial Exhaust Temp (IN) and Initial Exhaust Temp (OUT)" and read its value displayed on the intelligent tester.

Standard:
Same as the actual exhaust gas temperature (50 to 700°C [122 to 1,292°F] during idling after warm-up), and varies after an engine speed of 3,000 rpm is maintained for 1 minute.

Result:

Temperature Displayed	Proceed to
1,000°C (1,832°F)	A
0°C (32°F) (After warming up the engine)	B
OK: Same as the actual exhaust gas temperature (50 to 700°C [122 to 1,292°F] during idling after warm-up), and varies after maintaining the engine speed of 3,000 rpm for 1 minute after accelerating the engine from idling to 3,000 rpm	C

HINT:

If there is a short circuit, the intelligent tester will indicate 0°C (32°F).

If there is an open circuit, the intelligent tester will indicate 1,000°C (1,832°F).

Go to step 4

CHECK FOR INTERMITTENT PROBLEMS

A

2.CHECK EXHAUST GAS TEMPERATURE SENSOR (OPEN IN SENSOR)

Dtc P0544 Exhaust Gas Temperature Sensor Circuit (Bank 1 Sensor 1). 2AD-FHV ENGINE CONTROL SYSTEM. Lexus IS250 IS220d GSE20 ALE20

Disconnect the E72*1 or E73*2 exhaust gas temperature sensor connector.

*1: Upstream sensor

*2: Downstream sensor

Connect terminals 1 and 2 of the exhaust gas temperature sensor wire harness side connector.

Connect the intelligent tester to the DLC 3.

Turn the engine switch ON (IG) and turn the intelligent tester ON.

Enter the following menus: "Powertrain / Engine / Initial Exhaust Temp (IN) and Initial Exhaust Temp (OUT)" and read its value displayed on the intelligent tester.

Standard:
0°C (32°F)

Reconnect the exhaust gas temperature sensor connector.

REPLACE EXHAUST GAS TEMPERATURE SENSOR

NG

3.CHECK HARNESS AND CONNECTOR (EXHAUST GAS TEMPERATURE SENSOR - ECM)

Disconnect the E72*1 or E73*2 exhaust gas temperature sensor connector.

*1: Upstream sensor

*2: Downstream sensor

Disconnect the E59 ECM connector.

Check the resistance.

Standard resistance:
Tester Connections Specified Conditions
THCI (E73-2) - THCI (E59-122) Below 1 Ω
THCO (E72-2) - THCO (E59-121) Below 1 Ω
ETCI (E73-1) - ETCI (E59-99) Below 1 Ω
ETCO (E72-1) - ETCO (E59-98) Below 1 Ω

Reconnect the ECT sensor connector.

Reconnect the ECM connector

REPAIR OR REPLACE HARNESS OR CONNECTOR

REPLACE ECM

4.CHECK EXHAUST GAS TEMPERATURE SENSOR (SHORT IN SENSOR)

Disconnect the E72*1 or E73*2 exhaust gas temperature sensor connector.

*1: Upstream sensor

*2: Downstream sensor

Connect the intelligent tester to the DLC3.

Turn the engine switch ON (IG) and turn the intelligent tester ON.

Enter the following menus: "Powertrain / Engine / Initial Exhaust Temp (IN) and Initial Exhaust Temp (OUT)" and read its value displayed on the intelligent tester.

Standard:
1,000°C (1,832°F)

Reconnect the exhaust gas temperature sensor connector.

REPLACE EXHAUST GAS TEMPERATURE SENSOR

NG

5.CHECK HARNESS AND CONNECTOR (EXHAUST GAS TEMPERATURE SENSOR - ECM)

Disconnect the E72*1 or E73*2 exhaust gas temperature sensor connector.

*1: Upstream sensor

*2: Downstream sensor

Disconnect the E59 ECM connector.

Check the resistance.

Standard resistance:
Tester Connections Specified Conditions
THCI (E73-2) or THCI (E59-122) - Body ground 10 kΩ or higher
THCO (E72-2) or THCO (E59-121) - Body ground 10 kΩ or higher

Reconnect the ECT sensor connector.

Reconnect the ECM connector.

REPAIR OR REPLACE HARNESS OR CONNECTOR

REPLACE ECM

LEXUS IS250, IS220d / GSE20 ALE20

2AD-FHV ENGINE CONTROL SYSTEM

Lexus IS250 IS220d GSE20 ALE20

ECD SYSTEM

Tester Connections	Specified Conditions
THCI (E73-2) - THCI (E59-122)	Below 1 Ω
THCO (E72-2) - THCO (E59-121)	Below 1 Ω
ETCI (E73-1) - ETCI (E59-99)	Below 1 Ω
ETCO (E72-1) - ETCO (E59-98)	Below 1 Ω

Tester Connections	Specified Conditions
THCI (E73-2) or THCI (E59-122) - Body ground	10 kΩ or higher
THCO (E72-2) or THCO (E59-121) - Body ground	10 kΩ or higher