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:
Evaporative Emission Control System Incorrect Purge Flow
DTC SUMMARY
DESCRIPTION
The circuit description can be found in the EVAP (Evaporative Emission)
System (See page ES-409).
INSPECTION PROCEDURE
Refer to the EVAP System (See page ES-412).
MONITOR DESCRIPTION
The two monitors, Key-Off and Purge Flow, are used to detect malfunctions
relat ...
Antenna Coil Open / Short
DTC B2784 Antenna Coil Open / Short
DESCRIPTION
The transponder key coil is built into the transponder key amplifier and
receives a key code signal from
the transponder chip in the key. This signal is amplified by the amplifier, and
output to the transponder key
ECU.
DTC No.
...
How to proceed with
troubleshooting
NOTICE:
DTCs for the CAN communication system are as follows:
U0073, U0100, U0122, U0123, U0124, U0126 and U1101.
HINT:
If U0235 or U1102 is output alone, the CAN communication is
normal
1 CHECK AND CLEAR DTCS
HINT:
CAN communication DTCs are output when there is an
open or short in any ...