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 front of the cooler condenser assembly to detect the ambient temperature. Its signal is used for air conditioning control in AUTO mode. 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 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 air conditioning amplifier assembly applies a voltage (5 V) to the ambient temperature sensor (thermistor assembly) and reads voltage changes due to changes in the resistance of the ambient temperature sensor (thermistor assembly).

DTC No. DTC Detection Condition Trouble Area
B1412/12 Open or short in ambient temperature sensor (thermistor assembly) circuit
  • Ambient temperature sensor (thermistor assembly)

  • Harness or connector between ambient temperature sensor (thermistor assembly) and air conditioning amplifier assembly

  • Air conditioning amplifier assembly

WIRING DIAGRAM

A00064AE27
*a Ambient Temperature Sensor (Thermistor Assembly)
*b Air Conditioning Amplifier Assembly

PROCEDURE


  1. READ VALUE USING GTS


    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. Check the value(s) by referring to the table below.

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

      Ambient temperature sensor (thermistor assembly) /

      Min: -23.30°C (-9.94°F)

      Max: 65.95°C (150.71°F)

      Actual ambient temperature displayed -
      OK
      The display is as specified in the Normal Condition column.
      Result
      Result Proceed to
      NG A
      OK (When troubleshooting according to Problem Symptoms Table) B
      OK (When troubleshooting according to the DTC) C

    B
    C
    A
  2. INSPECT AMBIENT TEMPERATURE SENSOR (THERMISTOR ASSEMBLY)


    1. A000527E04
      A0008GFE04

      Remove the ambient temperature sensor (thermistor assembly) 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


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

      • 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).

      Text in Illustration
      *a

      Component without harness connected

      (Ambient Temperature Sensor (Thermistor Assembly))

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

    NG
    OK
  3. CHECK HARNESS AND CONNECTOR (AMBIENT TEMPERATURE SENSOR (THERMISTOR ASSEMBLY) - AIR CONDITIONING AMPLIFIER ASSEMBLY)


    1. Disconnect the H54 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
      H54-5 (TAM) - A3-2 (+) Always Below 1 Ω
      H54-13 (SG-2) - A3-1 (-) Always Below 1 Ω
      H54-5 (TAM) - Body ground Always 10 kΩ or higher
      H54-13 (SG-2) - Body ground Always 10 kΩ or higher

    OK
    NG