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
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 ai ...
Rear evaporator temperature sensor circuit
DESCRIPTION
The rear evaporator temperature sensor is installed on the rear evaporator.
It detects the rear evaporator
temperature. The sensor sends a signal to the A/C amplifier. The resistance o ...
Other materials:
Perform monitor drive pattern
The monitor results and test values can be checked with
the OBD II scan tool or the intelligent tester. The engine
control module (ECM) monitors the emissions-related
components such as the thermostat, catalyst converter
and evaporative emissions (EVAP), and determines
whether they are function ...
Inspection
1. INSPECT VANE PUMP SHAFT AND BUSHING IN VANE PUMP FRONT HOUSING
(a) Using a micrometer, measure the outer diameter [a]
of the vane pump shaft with pulley.
(b) Using vernier calipers, measure the inner diameter
[b] of the vane pump front housing bushing.
(c) Calculate the oil clearance ...
Confirmation of transmitter id registration
(a) Make sure that the ignition switch is off.
(b) Connect the intelligent tester to DLC3.
(c) Turn the ignition switch to the ON position.
(d) Select "TIREPRESS" by following the prompts
displayed on the intelligent tester.
(e) Confirm that the data of tire pressure of all ti ...
