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AIR CONDITIONING SYSTEM, Diagnostic DTC:B1412

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DTC Code DTC Name
B1412 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 (3.3 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 Ambient Temperature Sensor Circuit

  • Diagnosis condition: None

  • Malfunction status: Open or short in ambient temperature sensor circuit

  • Detection time: None (Present malfunction), continuously for 4 seconds or more (Past malfunction)

  • Thermistor assembly

  • Harness or connector

  • Air conditioning amplifier assembly

 Memorized
Tip:

If the ambient temperature is approximately -52.9°C (-63.22°F) or lower, DTC B1412 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


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    READ VALUE USING GTS (AMBIENT TEMP SENSOR)


    1. Connect the GTS to the DLC3.

    2. Turn the power 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

        Thermistor assembly system malfunction


        • When open circuit: -23.30°C (-9.94°F)

        • When short circuit: 65.95°C (150.71°F)



      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

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    INSPECT THERMISTOR ASSEMBLY


    1. Remove the thermistor assembly.

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    2. Inspect the thermistor assembly.

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      Result
      Proceed to
      OK
      NG

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


    1. Disconnect the G64 air conditioning amplifier assembly connector.

    2. Disconnect the A40 thermistor assembly connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      G64-13 (TAM) - A40-2 Always Below 1 Ω
      G64-2 (SG-2) - A40-1 Always Below 1 Ω
      G64-13 (TAM) or A40-2 - Other terminals and body ground Always 10 kΩ or higher
      G64-2 (SG-2) or A40-1 - Other terminals and 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