Toyota 4Runner: Room Temperature Sensor Circuit (B1411/11)

Toyota 4Runner Service Manual / Vehicle Interior / Heating / Air Conditioning / Air Conditioning System(for Automatic Air Conditioning System) / Room Temperature Sensor Circuit (B1411/11)

DESCRIPTION

The cooler thermistor (room temperature sensor) for the front seat is installed in the instrument panel to detect the room temperature and control the heater and air conditioner auto mode. The resistance of the room temperature sensor changes in accordance with the front room 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 room temperature sensor and reads voltage changes as the resistance of the room temperature sensor changes. This sensor also sends the appropriate signals to the air conditioning amplifier assembly.

DTC Code	DTC Detection Condition	Trouble Area
B1411/11	An open or short in the cooler thermistor (room temperature sensor) circuit.	Cooler thermistor (room temperature sensor) Harness or connector Air conditioning amplifier assembly

WIRING DIAGRAM

PROCEDURE

1.	READ VALUE USING TECHSTREAM (ROOM TEMPERATURE SENSOR)

(a) Use the Data List to check if the cooler thermistor (room temperature sensor) is functioning properly (See page ).

Air Conditioner

Tester Display	Measurement Item/Range	Normal Condition	Diagnostic Note
Room Temperature Sensor	Cooler thermistor (room temperature sensor) / Min.: -6.5°C (20.3°F) Max.: 57.25°C (135.05°F)	Actual room temperature for front seat displayed	Open in the circuit: -6.5°C (20.3°F). Short in the circuit: 57.25°C (135.05°F).

Tester Display

Measurement Item/Range

Normal Condition

Diagnostic Note

Room Temperature Sensor

Cooler thermistor (room temperature sensor) /

Min.: -6.5°C (20.3°F)

Max.: 57.25°C (135.05°F)

Actual room temperature for front seat displayed

Open in the circuit: -6.5°C (20.3°F).

Short in the circuit: 57.25°C (135.05°F).

OK:

The display is as specified in the normal condition column.

Result

Result	Proceed to
OK (When troubleshooting according to problem symptoms table)	A
OK (When troubleshooting according to the DTC)	B
NG	C

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

2.	INSPECT COOLER THERMISTOR (ROOM TEMPERATURE SENSOR)

(a) Remove the cooler thermistor (room temperature sensor) (See page ).

(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

Text in Illustration

*a	Sensing Portion
*b	Resistance
*c	Allowable Range
*d	Temperature

NOTICE:

Even slightly touching the sensor may change the resistance value. Be sure to hold the connector of the sensor.
When measuring, the sensor temperature must be the same as the ambient temperature.

HINT:

As the temperature increases, the resistance decreases (refer to the graph).

REPLACE COOLER THERMISTOR (ROOM TEMPERATURE SENSOR)

3.	CHECK HARNESS AND CONNECTOR (ROOM TEMPERATURE SENSOR - AIR CONDITIONING AMPLIFIER)

(a) Disconnect the F26 sensor connector.

(b) Disconnect the F42 amplifier connector.

Standard Resistance:

Tester Connection	Condition	Specified Condition
F26-1 - F42-29 (TR)	Always	Below 1 Ω
F26-2 - F42-34 (SG-1)	Always	Below 1 Ω
F42-29 (TR) - Body ground	Always	10 kΩ or higher
F42-34 (SG-1) - Body ground	Always	10 kΩ or higher

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

REPAIR OR REPLACE HARNESS OR CONNECTOR

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