AIR CONDITIONING SYSTEM(for Automatic Air Conditioning System), Diagnostic DTC:B1412/12

DTC Code DTC Name
B1412/12 Ambient Temperature Sensor Circuit

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 combination meter assembly and detects fluctuations in the ambient temperature. This data is used for controlling the cabin temperature. The sensor sends a signal to the combination meter 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 combination meter assembly applies a 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 combination meter assembly

  • Air conditioning amplifier assembly

  • Combination meter assembly

  • CAN communication system

Memorized

(4 sec. or more)*1

  • *1: The air conditioning amplifier assembly stores this DTC if the malfunction has occurred for the period of time indicated in the brackets.

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.

WIRING DIAGRAM

E270948E01

PROCEDURE

  1. READ VALUE USING GTS

    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    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.

      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

      -

      Body Electrical > Air Conditioner > Data List

      Tester Display

      Ambient Temp Sensor

      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

    PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

    Click hereClick hereClick hereClick hereClick here

    C

    REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

    Click hereClick hereClick here

    A

  2. INSPECT THERMISTOR ASSEMBLY

    1. E202729C19

      *a

      Component without harness connected

      (Thermistor Assembly)

      *b

      Sensing Portion

      *c

      Resistance (kΩ)

      *d

      Temperature (°C (°F))

      *e

      Allowable Range

      Remove the thermistor assembly.

      Click hereClick 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 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
    NG

    REPLACE THERMISTOR ASSEMBLY

    Click hereClick here

    OK

  3. CHECK HARNESS AND CONNECTOR (THERMISTOR ASSEMBLY - COMBINATION METER ASSEMBLY)

    1. Disconnect the E46 combination meter assembly connector.

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

      Standard Resistance

      Tester Connection

      Condition

      Specified Condition

      E46-35 (TX1+) - A23-2

      Always

      Below 1 Ω

      E46-34 (TX1-) - A23-1

      Always

      Below 1 Ω

      E46-35 (TX1+) - Body ground

      Always

      10 kΩ or higher

      E46-34 (TX1-) - Body ground

      Always

      10 kΩ or higher

    Result

    Proceed to

    OK

    NG
    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  4. REPLACE COMBINATION METER ASSEMBLY

    1. Replace the combination meter assembly.

      for Hatchback, Wagon:Click here

      for Sedan:Click hereClick here

      Tip:

      Since the combination meter assembly cannot be inspected while it is removed from the vehicle, replace the combination meter assembly with a new or known good one and check that the condition returns to normal.

    2. Check for DTCs.

      Click here

      Body Electrical > Air Conditioner > Trouble Codes

      Result

      Result

      Proceed to

      DTC B1412/12 is not output

      A

      DTC B1412/12 is output

      B
    A

    END (COMBINATION METER ASSEMBLY WAS DEFECTIVE)

    B

    REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

    Click hereClick hereClick here