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

DTC Code DTC Name
B1412/12 Ambient Temperature Sensor Circuit

DESCRIPTION

The cooler thermistor (ambient temperature sensor) is installed in the front part of the condenser assembly with receiver to detect the ambient temperature and control the air conditioning auto mode. The sensor connected to the air conditioning amplifier assembly 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 assembly. 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 combination meter assembly applies a voltage (5 V) to the cooler thermistor (ambient temperature sensor) and reads voltage changes as changes in the resistance of the cooler thermistor (ambient temperature sensor). The combination meter assembly sends the read signal to the air conditioning amplifier assembly via CAN communication.

DTC Code DTC Detection Condition Trouble Area
B1412/12 An open or short in the ambient temperature sensor circuit.

  • Cooler thermistor (ambient temperature sensor)

  • Harness or connector

  • Combination meter assembly

  • Air conditioning amplifier assembly

WIRING DIAGRAM

A0055UME16

PROCEDURE


  1. CHECK CAN COMMUNICATION SYSTEM


    1. Use the intelligent tester to check if the CAN communication system is functioning normally.

      OK
      CAN DTC is not output.

    NG

    GO TO CAN COMMUNICATION SYSTEM Click here

    OK

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


    1. Use the Data List to check if the cooler thermistor (ambient temperature sensor) is functioning properly.

      Air Conditioner
      Tester Display Measurement Item/Range Normal Condition Diagnostic Note
      Ambient Temp Sensor

      Ambient temperature sensor /

      Min: -23.3°C (-9.94°F)

      Max: 65.95°C (150.71°F)

      		 Actual ambient temperature displayed

      Open in the circuit: -23.3°C (-9.94°F).

      Short in the circuit: 65.95°C (150.71°F).
      OK
      The display is as specified in the normal condition column.
      Result
      Result Proceed to
      OK (When troubleshooting according to Problem Symptoms Table) A
      OK (When troubleshooting according to the DTC) B
      NG C

    A

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

    B

    REPLACE COMBINATION METER ASSEMBLY Click here

    C

  3. INSPECT COOLER THERMISTOR (AMBIENT TEMPERATURE SENSOR)


    1. Remove the ambient temperature sensor Click here.

      A00551XE01

    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

      Tech Tips

      As the temperature increases, the resistance decreases (Refer to the graph).

      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.

      Text in Illustration
      *1

      Component without harness connected

      (Ambient Temperature Sensor)
      *2 Sensing Portion
      *3 Resistance (kΩ)
      *4 Temperature °C (°F)
      *5 Allowable Range

    NG

    REPLACE COOLER THERMISTOR (AMBIENT TEMPERATURE SENSOR) Click here

    OK

  4. CHECK HARNESS AND CONNECTOR (AMBIENT TEMPERATURE SENSOR - COMBINATION METER)


    1. Disconnect the A19 sensor connector.

      A00540VE04

    2. Disconnect the D66 meter connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A19-1 - D66-34 (TEMP) Always Below 1 Ω
      A19-2 - D66-35 (TX1+)
      D66-34 (TEMP) - Body ground Always 10 kΩ or higher
      D66-35 (TX1+) - Body ground
      Text in Illustration
      *1

      Front view of wire harness connector

      (to Ambient Temperature Sensor)
      *2

      Rear view of wire harness connector

      (to Combination Meter Assembly)

    OK

    REPLACE COMBINATION METER ASSEMBLY Click here

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR