AIR CONDITIONING SYSTEM, Diagnostic DTC:B1412/12

DTC Code DTC Name
B1412/12 Ambient Temperature Sensor Circuit

DESCRIPTION

The ambient temperature sensor is installed in the front part of the condenser to detect the ambient temperature and control the air conditioner "AUTO" mode. The sensor connected to the front light ECU (front controller) 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 front light ECU (front controller). 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 front light ECU (front controller) applies voltage (5 V) to the ambient temperature sensor and reads voltage changes as the resistance of the ambient temperature sensor changes. The front light ECU (front controller) sends the read signal to the air conditioning amplifier via the CAN communication line.

Tech Tips

This circuit uses the CAN communication line. Before performing the inspection, check that the CAN communication system is functioning normally.

DTC No. DTC Detection Condition Trouble Area
B1412/12 Open or short in ambient temperature sensor circuit

  • Ambient temperature sensor

  • Harness and connector between ambient temperature sensor and front light ECU (front controller)

  • Front light ECU (front controller)

  • CAN communication line

  • Air conditioning amplifier

WIRING DIAGRAM

A001A8EE11

PROCEDURE


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


    1. Use the Data List to check if the 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 is displayed

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

      Short in circuit: 65.95°C (150.71°F)
      OK
      The display is as specified in the normal condition.
      Result
      Result Proceed to
      NG A
      OK (Checking from the PROBLEM SYMPTOMS TABLE) B
      OK (Checking from the DTC) C

    B

    PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE Click here

    C

    REPLACE AIR CONDITIONING AMPLIFIER Click here

    A

  2. INSPECT AMBIENT TEMPERATURE SENSOR

    A001CNPE01

    1. Remove the ambient temperature sensor Click here.

    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
      1 - 2 15°C (59°F) 2.45 to 2.88 kΩ
      1 - 2 20°C (68°F) 1.95 to 2.30 kΩ
      1 - 2 25°C (77°F) 1.60 to 1.80 kΩ
      1 - 2 30°C (86°F) 1.28 to 1.47 kΩ
      1 - 2 35°C (95°F) 1.00 to 1.22 kΩ
      1 - 2 40°C (104°F) 0.80 to 1.00 kΩ
      1 - 2 45°C (113°F) 0.65 to 0.85 kΩ
      1 - 2 50°C (122°F) 0.50 to 0.70 kΩ
      1 - 2 55°C (131°F) 0.44 to 0.60 kΩ
      1 - 2 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).


    NG

    REPLACE AMBIENT TEMPERATURE SENSOR Click here

    OK

  3. CHECK HARNESS AND CONNECTOR (AMBIENT TEMPERATURE SENSOR - FRONT LIGHT ECU)

    A0019FUE01
    *1 Front view of wire harness connector: (to Ambient Temperature Sensor)
    *2 Front view of wire harness connector: (to Front Light ECU)
    *3 TM

    1. Disconnect the B5 ambient temperature sensor connector.

    2. Disconnect the B14 front light ECU connector.

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

      Standard resistance
      Tester Connection Condition Specified Condition
      B5-1 - B14-20 (TM) Always Below 1 Ω
      B5-2 - B14-19 (TME) Always Below 1 Ω
      B14-20 (TM)- Body ground Always 10 kΩ or higher
      B14-19 (TME) - Body ground Always 10 kΩ or higher

    OK

    REPLACE FRONT LIGHT ECU

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR