Toyota Tundra Service Manual: Ambient Temperature Sensor Circuit (B1412/12)

Toyota Tundra Service Manual / Vehicle Interior / Air Conditioning / Air Conditioning System(for Manual Air Conditioning System) / Ambient Temperature Sensor Circuit (B1412/12)

DESCRIPTION

The ambient temperature sensor is installed in front of the condenser to detect the ambient temperature. This sensor is connected to the air conditioning amplifier and detects fluctuations in the ambient temperature. This data is used for controlling the cabin temperature. The sensor sends a signal to the air conditioning amplifier. The resistance of the ambient temperature sensor changes in accordance with the ambient temperature. As the temperature decreases, the resistance increases. As the temperature increases, the resistance decreases.

The air conditioning amplifier applies voltage (5 V) to the ambient temperature sensor and reads voltage changes as the resistance of the ambient temperature sensor changes.

DTC Code	DTC Detection Condition	Trouble Area
B1412/12	Open or short in ambient temperature sensor circuit	Ambient temperature sensor Harness or connector between ambient temperature sensor and air conditioning amplifier Air conditioning amplifier

WIRING DIAGRAM

PROCEDURE

1.	READ VALUE USING TECHSTREAM (AMBIENT TEMPERATURE SENSOR)

(a) Use the Data List to check if the ambient temperature sensor is functioning properly.

Air Conditioner

Tester Display

Measurement Item / Range

Normal Condition

Diagnostic Note

Ambient Temp Sensor

Ambient temperature sensor /

Min.: -23.3°C (-9.94°F)

Max.: 65.95°C (150.71°F)

Actual ambient temperature is displayed

Open in circuit: -23.3°C (-9.94°F)

Short in circuit: 65.95°C (150.71°F)

OK:

The display is as specified in the normal condition.

Result

Result	Proceed to
NG	A
OK (Checking from the PROBLEM SYMPTOMS TABLE)	B
OK (Checking from the DTC)	C

PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE

REPLACE AIR CONDITIONING AMPLIFIER

2.	INSPECT AMBIENT TEMPERATURE SENSOR

(a) Remove the ambient 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

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 (see the graph).

REPLACE AMBIENT TEMPERATURE SENSOR

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

(a) Disconnect the A15 sensor connector.

(b) Disconnect the J19 air conditioning amplifier connector.

Standard resistance:

Tester Connection	Condition	Specified Condition
A15-1 - J19-5 (TAM)	Always	Below 1 Ω
A15-2 - J19-13 (SG-2)	Always	Below 1 Ω
A15-1 or J19-5 (TAM) - Body ground	Always	10 kΩ or higher
A15-2 or J19-13 (SG-2) - Body ground	Always	10 kΩ or higher

REPLACE AIR CONDITIONING AMPLIFIER

REPAIR OR REPLACE HARNESS OR CONNECTOR

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