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:
Removal
1. REMOVE GLOVE COMPARTMENT DOOR STOPPER
SUB-ASSEMBLY
2. REMOVE GLOVE COMPARTMENT DOOR
ASSEMBLY
3. REMOVE STEREO COMPONENT AMPLIFIER
ASSEMBLY (W/ STEREO COMPONENT AMPLIFIER)
4. REMOVE DISTANCE CONTROL ECU ASSEMBLY
Remove the bolt.
Disengage the clip and remove the distanc ...
Inspection
1. INSPECT POWER STEERING RACK
(a) Using a dial indicator, check the power steering rack
for runout and for teeth wear and damage.
Maximum runout:
0.3 mm (0.012 in.)
If necessary, replace the rack & pinion power
steering gear assembly.
(b) Check the back surface for wear and damag ...
Check for intermittent
problems
1. CHECK FOR INTERMITTENT PROBLEMS
HINT:
For use of the intelligent tester only:
Inspect the vehicle's ECM using check mode.
Intermittent problems are easier to detect with an
intelligent tester when the ECM is in check mode. In
check mode, the ECM uses 1 trip detection logic, which
is more ...