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 cooler condenser assembly 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 cooler thermistor (ambient temperature sensor) changes in accordance with the cooler thermistor temperature (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 cooler thermistor (ambient temperature sensor) and reads voltage changes as changes in the resistance of the cooler thermistor (ambient temperature sensor).

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

Memory

Note

B1412/12

Ambient Temperature Sensor Circuit

An open or short in the cooler thermistor (ambient temperature sensor) circuit.

  • Cooler thermistor (ambient temperature sensor)

  • Harness or connector

  • Air conditioning amplifier assembly

Stored

(4 seconds or more)

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

WIRING DIAGRAM

E193111E15

PROCEDURE

  1. 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

      Click here

      OK

      The display is as specified in the normal condition column.

      Body Electrical > Air Conditioner > Data List

      Tester Display

      Measurement Item

      Range

      Normal Condition

      Diagnostic Note

      Ambient Temp Sensor

      Cooler thermistor (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).

    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 AIR CONDITIONING AMPLIFIER ASSEMBLY

    Click here

    C

  2. INSPECT COOLER THERMISTOR (AMBIENT TEMPERATURE SENSOR)

    1. Remove the cooler thermistor (ambient temperature sensor)

      Click here

      E252331C01

      *a

      Sensing Portion

      *b

      Resistance

      *c

      Allowable Range

      *d

      Temperature

    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:

      • 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.

      Tip:

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

    Result

    Result

    OK

    NG
    NG

    REPLACE COOLER THERMISTOR (AMBIENT TEMPERATURE SENSOR)

    Click here

    OK

  3. CHECK HARNESS AND CONNECTOR (AMBIENT TEMPERATURE SENSOR - AIR CONDITIONING AMPLIFIER)

    1. Disconnect the A1 sensor connector.

    2. Disconnect the G13 amplifier connector.

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

      Standard Resistance

      Tester Connection

      Condition

      Specified Condition

      A1-1 - G13-5 (TAM)

      Always

      Below 1 Ω

      A1-2 - G13-13 (SG-2)

      G13-5 (TAM) - Body ground

      Always

      10 kΩ or higher

      G13-13 (SG-2) - Body ground

    Result

    Result

    OK

    NG
    OK

    REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

    Click here

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR