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AIR CONDITIONING SYSTEM, Diagnostic DTC:B1412/12

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DTC Code DTC Name
B1412/12 Ambient Temperature Sensor Circuit
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DESCRIPTION

The thermistor assembly is installed in front of the cooler condenser assembly to detect the ambient temperature, which is used to control the air conditioning system. This sensor is connected to the air conditioning amplifier assembly and detects fluctuations in the ambient temperature. This data is used for controlling the cabin temperature. The sensor sends a signal to the air conditioning amplifier assembly. The resistance of the thermistor assembly changes in accordance with the ambient temperature. As the temperature decreases, the resistance increases. As the temperature increases, the resistance decreases.

The air conditioning amplifier assembly applies voltage (5 V) to the thermistor assembly and reads voltage changes due to changes in the resistance of the thermistor assembly.

DTC No. Detection Item DTC Detection Condition Trouble Area Memory
B1412/12 Ambient Temperature Sensor Circuit Open or short in ambient temperature sensor circuit

  • Thermistor assembly

  • Harness or connector between thermistor assembly and air conditioning amplifier assembly

  • Air conditioning amplifier assembly

Memorized

(4 sec. or more)*

Tip:

If the ambient temperature is approximately -52.9°C (-63.22°F) or lower, DTC B1412/12 may be output even though the system is normal.

Table 1. *a Thermistor Assembly *b Air Conditioning Amplifier Assembly
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WIRING DIAGRAM

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PROCEDURE


  1. Click here

    READ VALUE USING GTS


    1. Connect the GTS to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the GTS on.

    4. Enter the following menus: Body Electrical / Air Conditioner / Data List.

    5. Read the Data List according to the display on the GTS.


      1. Body Electrical > Air Conditioner > Data List
        Tester Display Measurement Item Range Normal Condition Diagnostic Note
        Ambient Temp Sensor Thermistor assembly

        Min.: -23.30°C (-9.94°F)

        Max.: 65.95°C (150.71°F)

        		 Actual ambient temperature displayed -



      1. Body Electrical > Air Conditioner > Data List
        Tester Display
        Ambient Temp Sensor




      OK
      The display is as specified in the normal condition column.
      Result
      Proceed to
      OK
      NG

  2. Click here

    INSPECT THERMISTOR ASSEMBLY


    1. A01FNHNC29
      *a

      Component without harness connected

      (Thermistor Assembly)
      *b Sensing Portion
      *c Resistance (kΩ)
      *d Temperature (°C (°F))
      *e Allowable Range

      Remove the thermistor assembly.

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    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:

      • Hold the sensor only by its connector. Touching the sensing portion may change the resistance value.

      • When measuring, the sensor temperature must be the same as the ambient temperature.

      Tip:

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

      Result
      Proceed to
      OK
      NG

  3. Click here

    CHECK HARNESS AND CONNECTOR (THERMISTOR ASSEMBLY - AIR CONDITIONING AMPLIFIER ASSEMBLY)


    1. Disconnect the O10 air conditioning amplifier assembly connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      O10-10 (TAM) - B5-1 (+) Always Below 1 Ω
      O10-32 (SG-2) - B5-2 (-) Always Below 1 Ω
      O10-10 (TAM) - Body ground Always 10 kΩ or higher
      O10-32 (SG-2) - Body ground Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    • OK

      REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLYClick here

    • NG

      REPAIR OR REPLACE HARNESS OR CONNECTOR