AIR CONDITIONING SYSTEM (for Automatic Air Conditioning System), Diagnostic DTC:B1412/12

DTC Code DTC Name
B1412/12 Ambient Temperature Sensor Circuit

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

  • Open or short in ambient temperature sensor circuit

  • Data communication from ambient temperature sensor interrupted

  • Ambient temperature sensor (thermistor assembly)

  • Harness and connector between ambient temperature sensor (thermistor assembly) and combination meter assembly

  • Combination meter assembly

  • Air conditioning amplifier

  • CAN communication line

WIRING DIAGRAM

A011BSIE01

INSPECTION PROCEDURE

PROCEDURE


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


    1. Connect the intelligent tester to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the intelligent tester on.

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

    5. 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

    REPLACE COMBINATION METER ASSEMBLY Click here

    A

  2. INSPECT AMBIENT TEMPERATURE SENSOR (THERMISTOR ASSEMBLY)

    A011ATDE39

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

    2. 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

      Note


      • 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.

      Tech Tips

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

    3. 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)

    A011823E02
    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)

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

    2. Disconnect the D1 combination meter assembly connector.

    3. 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

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

    5. Reconnect the combination meter assembly connector.


    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.

      Tech Tips

      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.

    2. 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