Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Room Temperature Sensor Circuit (B1411/11)

Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual / Vehicle Interior / Heating / Air Conditioning / Air Conditioning System / Room Temperature Sensor Circuit (B1411/11)

DESCRIPTION

The cooler (room temp. sensor) thermistor is installed in the instrument panel to detect the cabin temperature, which is used to control the air conditioning system. The resistance of the cooler (room temp. sensor) thermistor changes in accordance with the cabin temperature. As the temperature decreases, the resistance increases. As the temperature increases, the resistance decreases.

The air conditioning amplifier assembly applies voltage (5 V) to the cooler (room temp. sensor) thermistor and reads voltage changes due to changes in the resistance of the cooler (room temp. sensor) thermistor.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

Memory

B1411/11

Room Temperature Sensor Circuit

Open or short in room temperature sensor circuit
  • Cooler (room temp. sensor) thermistor
  • Harness or connector between cooler (room temp. sensor) thermistor and air conditioning amplifier assembly
  • Air conditioning amplifier assembly

Memorized

(4 sec. or more)*
  • *: The air conditioning amplifier assembly stores this DTC if the malfunction has occurred for the period of time indicated in the brackets.

HINT:

If the cabin temperature is approximately -18.6°C (-1.48°F) or lower, DTC B1411/11 may be output even though the system is normal.

WIRING DIAGRAM

PROCEDURE

1.

READ VALUE USING TECHSTREAM

(a) Connect the Techstream to the DLC3.

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

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / Air Conditioner / Data List.

(e) Read the Data List according to the display on the Techstream.

Body Electrical > Air Conditioner > Data List

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Room Temperature Sensor

Cooler (room temp. sensor) thermistor

Min.: -6.50°C (20.30°F)

Max.: 57.25°C (135.05°F)

Actual cabin temperature displayed

-
Body Electrical > Air Conditioner > Data List

Tester Display

Room Temperature Sensor

OK:

The display is as specified in the normal condition column.

Result

Proceed to

NG

A

OK (When troubleshooting according to Problem Symptoms Table)

B

OK (When troubleshooting according to the DTC)

C
B

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

C

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

A

2.

INSPECT COOLER (ROOM TEMP. SENSOR) THERMISTOR

(a) Remove the cooler (room temp. sensor) thermistor.

Click here

*a

Component without harness connected

(Cooler (Room Temp. Sensor) Thermistor)

*b

Sensing Portion

*c

Resistance (kΩ)

*d

Temperature (°C (°F))

*e

Allowable Range

(b) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection

Condition

Specified Condition

1 - 2

10°C (50°F)

3.00 to 3.73 kΩ

15°C (59°F)

2.45 to 2.88 kΩ

20°C (68°F)

1.95 to 2.30 kΩ

25°C (77°F)

1.60 to 1.80 kΩ

30°C (86°F)

1.28 to 1.47 kΩ

35°C (95°F)

1.00 to 1.22 kΩ

40°C (104°F)

0.80 to 1.00 kΩ

45°C (113°F)

0.65 to 0.85 kΩ

50°C (122°F)

0.50 to 0.70 kΩ

55°C (131°F)

0.44 to 0.60 kΩ

60°C (140°F)

0.36 to 0.50 kΩ

NOTICE:

  • Hold the sensor only by its connector. Touching the sensing portion may change the resistance value.
  • When measuring, the sensor temperature must be the same as the ambient temperature.

HINT:

As the temperature increases, the resistance decreases (see the graph).

NG

REPLACE COOLER (ROOM TEMP. SENSOR) THERMISTOR

OK

3.

CHECK HARNESS AND CONNECTOR (COOLER (ROOM TEMP. SENSOR) THERMISTOR - AIR CONDITIONING AMPLIFIER ASSEMBLY)

(a) Disconnect the J42 air conditioning amplifier assembly connector.

(b) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection

Condition

Specified Condition

J42-14 (TR) - J16-1

Always

Below 1 Ω

J42-1 (SG-1) - J16-2

Always

Below 1 Ω

J42-14 (TR) or J16-1 - Body ground

Always

10 kΩ or higher

J42-1 (SG-1) or J16-2 - Body ground

Always

10 kΩ or higher
OK

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
    Data List / Active Test
    DATA LIST / ACTIVE TEST DATA LIST NOTICE: In the table below, the values listed under "Normal Condition" are reference values. Do not depend solely on these reference values when deciding whether a pa ...

    Diagnostic Trouble Code Chart
    DIAGNOSTIC TROUBLE CODE CHART Air Conditioning System DTC No. Detection Item DTC Detection Condition Link B1411/11 Room Temperature Sensor Circuit Open or short in room temperature se ...

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