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 condenser to detect the ambient temperature which is used to control the air conditioning system 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 to 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

B000H9WE03

INSPECTION PROCEDURE

PROCEDURE


  1. READ VALUE USING INTELLIGENT TESTER


    1. Connect the intelligent tester to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the intelligent tester on.

    4. Enter the following menus: Body / 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 (for TMC, TMMR Made)) C
      OK (When troubleshooting according to the DTC (for TMMK Made)) D

    B

    PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE Click here

    C

    REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY Click here

    D

    REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY Click here

    A

  2. INSPECT AMBIENT TEMPERATURE SENSOR (THERMISTOR ASSEMBLY)


    1. Remove the ambient temperature sensor (thermistor assembly) Click here.

    2. B000KAEE15
      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))

      Disconnect the A3 ambient temperature sensor (thermistor assembly) connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A3-1 (-) - A3-2 (+) 10°C (50°F) 3.00 to 3.73 kΩ
      A3-1 (-) - A3-2 (+) 15°C (59°F) 2.45 to 2.88 kΩ
      A3-1 (-) - A3-2 (+) 20°C (68°F) 1.95 to 2.30 kΩ
      A3-1 (-) - A3-2 (+) 25°C (77°F) 1.60 to 1.80 kΩ
      A3-1 (-) - A3-2 (+) 30°C (86°F) 1.28 to 1.47 kΩ
      A3-1 (-) - A3-2 (+) 35°C (95°F) 1.00 to 1.22 kΩ
      A3-1 (-) - A3-2 (+) 40°C (104°F) 0.80 to 1.00 kΩ
      A3-1 (-) - A3-2 (+) 45°C (113°F) 0.65 to 0.85 kΩ
      A3-1 (-) - A3-2 (+) 50°C (122°F) 0.50 to 0.70 kΩ
      A3-1 (-) - A3-2 (+) 55°C (131°F) 0.44 to 0.60 kΩ
      A3-1 (-) - A3-2 (+) 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).


    NG

    REPLACE AMBIENT TEMPERATURE SENSOR (THERMISTOR ASSEMBLY) Click here

    OK

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


    1. Disconnect the I77 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
      I77-5 (TAM) - A3-2 (+) Always Below 1 Ω
      I77-13 (SG-2) - A3-1 (-) Always Below 1 Ω
      I77-5 (TAM) - Body ground Always 10 kΩ or higher
      I77-13 (SG-2) - Body ground Always 10 kΩ or higher
      Result
      Result Proceed to
      OK (for TMC, TMMR Made) A
      OK (for TMMK Made) B
      NG C

    B

    REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY Click here

    C

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    A

    REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY Click here