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:
Disassembly
1. REMOVE RH SEAT REAR SEAT RECLINING COVER
Remove the 2 screws.
Remove the RH seat rear seat reclining cover by
pulling it out in the arrow mark direction shown in
the illustration.
2. REMOVE LH SEAT REAR SEAT RECLINING COVER
Remove the 2 screws.
R ...
Active Control Engine Mount System
DESCRIPTION
LOCATION
The Active Control Engine Mount (ACM) system decreases engine vibration at
engine idling using the
ACM VSV. The VSV is controlled by a pulse signal transmitted to the VSV from the
ECM. The frequency
of this pulse signal is matched to the engine speed to decrease engi ...
ECM / PCM Internal Engine Off Timer Performance
DTC SUMMARY
DESCRIPTION
To ensure the accuracy of the EVAP (Evaporative Emission) monitor values, the
soak timer, which is built
into the ECM, measures 5 hours (+/- 15 minutes) from when the ignition switch is
turned off, before the
monitor is run. This allows the fuel to cool down, whic ...
