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
Room Temperature Sensor Circuit
DESCRIPTION
This sensor detects the cabin temperature that is used as the basis for
temperature control and sends a
signal to the A/C amplifier.
WIRING DIAGRAM
INSPECTION PROCEDURE
1 READ VAL ...
Evaporator temperature sensor circuit
DESCRIPTION
The evaporator temperature sensor (A/C thermistor) is installed on the
evaporator in the air conditioning
unit. It detects the temperature of the cooled air that has passed through the ...
Other materials:
Unlocking and locking the doors from the outside
Entry function (vehicles with a smart key system)
Carry the electronic key to enable this function.
Grip the driver’s door handle
to unlock the door. Grip the
passenger’s door handle to
unlock all the doors.*
Make sure to touch the sensor
on the back of the handle.
The doors ...
On-vehicle inspection
1. INSPECT FRONT PASSENGER AIRBAG ASSEMBLY
(VEHICLE NOT INVOLVED IN COLLISION)
Perform a diagnostic system check.
With the front passenger airbag assembly installed
on the vehicle, perform a visual check. If there are
any defects as mentioned below, replace the
instrumen ...
Fail-safe chart
HINT:
If the following conditions are detected while the cruise
control is in operation, the system clears the stored vehicle
speed in the ECM and cancels the cruise control operation.
Vehicle Condition
Auto Cancel Condition
Re-operation Condition
CRUISE main in ...
