Toyota Sienna Service Manual: Ambient temperature sensor circuit

DTC B1412/12 Ambient Temperature Sensor Circuit

DESCRIPTION

The ambient temperature sensor is installed in front of the condenser to detect the ambient temperature which is used to control the air conditioner "AUTO" mode. This sensor is connected to the A/C amplifier and detects fluctuations in the ambient temperature. This data is used for controlling the cabin temperature. The sensor sends a signal to the A/C 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 A/C amplifier applies voltage (5 V) to the ambient temperature sensor and reads voltage changes as the resistance of the ambient temperature sensor changes.

WIRING DIAGRAM

INSPECTION PROCEDURE

1 READ VALUE OF INTELLIGENT TESTER

(a) Connect the intelligent tester to the DLC3.

(b) Turn the ignition switch to the ON position and turn the intelligent tester main switch on.

(c) Select the item below in the DATA LIST, and read the display on the intelligent tester.

DATA LIST / AIR CONDITIONER:

OK: The display is as specified in the normal condition column.

Result

2 INSPECT AMBIENT TEMPERATURE SENSOR

(a) Remove the ambient temperature sensor.

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

Standard resistance

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).

3 CHECK HARNESS AND CONNECTOR (AMBIENT TEMPERATURE SENSOR - A/C AMPLIFIER)

(a) Disconnect the ambient temperature sensor connector.

(b) Disconnect the A/C amplifier connector.

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

Standard resistance

REPLACE A/C AMPLIFIER