DTC    B1412/12    Ambient Temperature Sensor Circuit

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DESCRIPTION

The ambient temperature sensor (thermistor assembly) is installed in the front part of the condenser to detect the ambient temperature and control the air conditioner. The sensor is connected to the combination meter assembly and detects fluctuations in the ambient temperature. This data is used for controlling the room temperature. The sensor sends a signal to the air conditioning amplifier via the combination meter assembly. The resistance of the ambient temperature sensor (thermistor assembly) changes in accordance with the ambient temperature. As the temperature decreases, the resistance increases. As the temperature increases, the resistance decreases.
The combination meter assembly applies a voltage (5 V) to the ambient temperature sensor (thermistor assembly) and reads voltage changes as changes in the resistance of the ambient temperature sensor (thermistor assembly). The combination meter assembly sends the read signal to the air conditioning amplifier via CAN communications.

DTC No.
DTC Detection Condition
Trouble Area
B1412/12
  1. Open or short in ambient temperature sensor circuit
  2. Data communication from ambient temperature sensor interrupted
  1. Ambient temperature sensor (thermistor assembly)
  2. Harness and connector between ambient temperature sensor (thermistor assembly) and combination meter assembly
  3. Combination meter assembly
  4. Air conditioning amplifier
  5. CAN communication line

WIRING DIAGRAM


E181438E01


INSPECTION PROCEDURE

1.READ VALUE USING INTELLIGENT TESTER (AMBIENT TEMPERATURE SENSOR)

  1. Connect the intelligent tester to the DLC3.

  1. Turn the ignition switch to ON.

  1. Turn the intelligent tester on.

  1. Enter the following menus: Body / Combination Meter / Data List.

  1. According to the display on the intelligent tester, read the Data List.

    Combination Meter 
    Item
    		Measurement Item/Display (Range)
    		Normal Condition
    		Diagnostic Note
    Ambient Temperature Sensor
    		Ambient temperature sensor /
    Min.: -40°C (-40°F)
    Max.: 87.5°C (189.5°F)
    		Actual ambient temperature is displayed
    		-

    OK:
    The display is as specified in the normal condition column.


    Result 
    Result
    		Proceed to
    NG
    		A
    OK (When troubleshooting according to the Problem Symptoms Table)
    		B
    OK (When troubleshooting according to the DTC output)
    		C



B
PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE (Click here)

C
Go to step 4
A


2.INSPECT AMBIENT TEMPERATURE SENSOR (THERMISTOR ASSEMBLY)
E118395E39

  1. Remove the ambient temperature sensor (thermistor assembly).

  1. Measure the resistance according to the value(s) in the table below.

    Standard Resistance:
    Tester Connection
    		Condition
    		Specified Condition
    1 - 2
    		10°C (50°F)
    		3.00 to 3.73 kΩ
    15°C (59°F)
    		2.45 to 2.88 kΩ
    20°C (68°F)
    		1.95 to 2.30 kΩ
    25°C (77°F)
    		1.60 to 1.80 kΩ
    30°C (86°F)
    		1.28 to 1.47 kΩ
    35°C (95°F)
    		1.00 to 1.22 kΩ
    40°C (104°F)
    		0.80 to 1.00 kΩ
    45°C (113°F)
    		0.65 to 0.85 kΩ
    50°C (122°F)
    		0.50 to 0.70 kΩ
    55°C (131°F)
    		0.44 to 0.60 kΩ
    60°C (140°F)
    		0.36 to 0.50 kΩ

    NOTICE:
    1. Even slightly touching the sensor may change the resistance value. Be sure to hold the connector of the sensor.
    2. When measuring, the sensor temperature must be the same as the ambient temperature.

    HINT:
    As the temperature increases, the resistance decreases (See the graph).

  1. Reinstall the ambient temperature sensor (thermistor assembly).



NG
REPLACE AMBIENT TEMPERATURE SENSOR (THERMISTOR ASSEMBLY) (Click here)
OK


3.CHECK HARNESS AND CONNECTOR (AMBIENT TEMPERATURE SENSOR - COMBINATION METER ASSEMBLY)
E120284E02

  1. Disconnect the A25 ambient temperature sensor (thermistor assembly) connector.

  1. Disconnect the D1 combination meter assembly connector.

  1. Measure the resistance according to the value(s) in the table below.

    Standard Resistance:
    Tester Connection
    		Condition
    		Specified Condition
    A25-2 - D1-4 (TX1-)
    		Always
    		Below 1 Ω
    A25-1 - D1-23 (TX1+)
    		Always
    		Below 1 Ω
    A25-2 - Body ground
    		Always
    		1 MΩ or higher
    A25-1 - Body ground
    		Always
    		1 MΩ or higher

  1. Reconnect the ambient temperature sensor (thermistor assembly) connector.

  1. Reconnect the combination meter assembly connector.
    Text in Illustration 
    *1
    		Front view of wire harness connector
    (to Ambient Temperature Sensor (Thermistor Assembly))
    *2
    		Rear view of wire harness connector
    (to Combination Meter Assembly)



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

REPLACE COMBINATION METER ASSEMBLY (Click here)  

4.REPLACE COMBINATION METER ASSEMBLY

  1. Replace the combination meter assembly (Click here).

    HINT:
    Since the combination meter assembly cannot be inspected while it is removed from the vehicle, replace the combination meter assembly with a normal one and check that the condition returns to normal.


NEXT


5.CHECK FOR DTC

  1. Clear the DTC (Click here).

  1. Check for DTCs (Click here).
    Result 
    Result
    		Proceed to
    DTC B1412 is not output
    		A
    DTC B1412 is output
    		B



B
REPLACE AIR CONDITIONING AMPLIFIER (Click here)
A

END