Toyota Sienna Service Manual: 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 evaporator and its signal is used to control the air conditioning. It sends a signal to the A/C amplifier. The resistance of the evaporator temperature sensor (A/C thermistor) changes in accordance with the temperature of the cooled air that has passed through the evaporator. As the temperature decreases, the resistance increases. As the temperature increases, the resistance decreases.
The A/C amplifier applies voltage (5 V) to the evaporator temperature sensor
(A/C thermistor) and reads
voltage changes as the resistance of the evaporator temperature sensor (A/C
thermistor) changes. This
sensor is used to prevent the evaporator from freezing.
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 EVAPORATOR TEMPERATURE SENSOR
(a) Disconnect the connector from the evaporator 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 evaporator temperature.
HINT: As the temperature increases, the resistance decreases (see the graph).
3 CHECK HARNESS AND CONNECTOR (EVAPORATOR TEMPERATURE SENSOR - A/C AMPLIFIER)
(a) Disconnect the evaporator 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
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DESCRIPTION
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Rear evaporator temperature sensor circuit
DESCRIPTION
The rear evaporator temperature sensor is installed on the rear evaporator.
It detects the rear evaporator
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Other materials:
Disassembly
1. REMOVE REAR NO. 2 SEAT COVER BEZEL
Remove the 5 screws.
Disengage the 5 claws and remove the rear No. 2
seat cover bezel.
2. REMOVE REAR SEAT RECLINING COVER LH
Remove the 2 screws.
Disengage the claw and remove the rear seat
reclining cover LH.
...
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DESCRIPTION
The rear airbag sensor LH circuit consists of the center airbag sensor
assembly and rear airbag sensor
LH.
If the center airbag sensor assembly receives signals from the rear airbag
sensor LH, it judges whether or
not the ...
Rear ceiling lights
Turns the lights on/off
When the personal/interior light
main switch is in the off position,
the rear ceiling lights will not turn
on even if the switch is on.
Adjusting the rear personal/interior lights angle (if equipped)
Push the edge of the light lens.
Illuminated entry system
...
