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

Tech Tips

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

A01TDPKE01
*a Thermistor Assembly
*b Combination Meter Assembly
*c Air Conditioning Amplifier Assembly
*d CAN Communication Line

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 here

    C

    REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY Click here

    A

  2. INSPECT THERMISTOR ASSEMBLY


    1. A01TCRMC19
      *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 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.

      Tech Tips

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

      Result
      Proceed to
      OK
      NG

    NG

    REPLACE THERMISTOR ASSEMBLY Click 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.

      Click here

      Tech Tips

      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