AIR CONDITIONING SYSTEM(for Automatic Air Conditioning System), Diagnostic DTC:B1304

DTC Code DTC Name
B1304 Evaporator Probe Fault

DESCRIPTION

The No. 1 cooler thermistor is installed on the evaporator in the air conditioner unit to detect the temperature of the cooled air that has passed through the evaporator, which is used to control the air conditioning system. It sends signals to the air conditioning control assembly. The resistance of the No. 1 cooler thermistor changes in accordance with the temperature of the cooled air that has passed through the evaporator. As the temperature decreases, the resistance increases. As the temperature increases, the resistance decreases.

The air conditioning control assembly applies voltage (5 V) to the No. 1 cooler thermistor and reads voltage changes as the resistance of the No. 1 cooler thermistor changes. This sensor is used for frost prevention.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

B1304

Evaporator Probe Fault

Open or short in evaporator temperature sensor circuit

  • No. 1 cooler thermistor

  • Air conditioning harness assembly between No. 1 cooler thermistor and air conditioning control assembly

  • Air conditioning control assembly

WIRING DIAGRAM

E229251E47

PROCEDURE

  1. CHECK AIR CONDITIONING HARNESS ASSEMBLY (NO. 1 COOLER THERMISTOR - AIR CONDITIONING CONTROL ASSEMBLY)

    1. Disconnect the P1 air conditioning control assembly connector.

    2. Disconnect the P6 No. 1 cooler thermistor connector.

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

      Standard Resistance

      Tester Connection

      Condition

      Specified Condition

      P6-1 - P1-15 (TEMP EVAPO IN)

      Always

      Below 1 Ω

      P6-2 - P1-24 (GND EVAPO)

      Always

      Below 1 Ω

      P6-1 - Body ground

      Always

      10 kΩ or higher

      P6-2 - Body ground

      Always

      10 kΩ or higher

    Result

    Proceed to

    OK

    NG
    NG

    REPLACE AIR CONDITIONING HARNESS ASSEMBLY

    Click here

    OK

  2. INSPECT NO. 1 COOLER THERMISTOR

    1. Remove the No. 1 cooler thermistor.

      Click here

      E293839C01

      *a

      Component without harness connected

      (No. 1 Cooler Thermistor)

      *b

      Sensing Portion

      *c

      Resistance (kΩ)

      *d

      Temperature (°C (°F))

      *e

      Allowable Range

      -

      -

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

      Standard Resistance

      Tester Connection

      Condition

      Specified Condition

      1 - 2

      -30°C (-22°F)

      47.59 to 49.99 kΩ

      -25°C (-13°F)

      35.12 to 36.76 kΩ

      -20°C (-4°F)

      26.19 to 27.33 kΩ

      -15°C (5°F)

      19.71 to 20.50 kΩ

      -10°C (14°F)

      14.97 to 15.53 kΩ

      -5°C (23°F)

      11.47 to 11.86 kΩ

      0°C (32°F)

      8.87 to 9.14 kΩ

      5°C (41°F)

      6.88 to 7.12 kΩ

      10°C (50°F)

      5.39 to 5.59 kΩ

      15°C (59°F)

      4.25 to 4.41 kΩ

      20°C (68°F)

      3.37 to 3.51 kΩ

      25°C (77°F)

      2.70 to 2.82 kΩ

      30°C (86°F)

      2.17 to 2.27 kΩ

      35°C (95°F)

      1.76 to 1.84 kΩ

      40°C (104°F)

      1.43 to 1.51 kΩ

      45°C (113°F)

      1.17 to 1.24 kΩ

      50°C (122°F)

      0.97 to 1.02 kΩ

      55°C (131°F)

      0.80 to 0.85 kΩ

      60°C (140°F)

      0.66 to 0.71 kΩ

      65°C (149°F)

      0.56 to 0.59 kΩ

      70°C (158°F)

      0.47 to 0.50 kΩ

      75°C (167°F)

      0.40 to 0.42 kΩ

      80°C (176°F)

      0.34 to 0.36 kΩ

      85°C (185°F)

      0.29 to 0.31 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

    Result

    Proceed to

    OK (When troubleshooting according to the DTC)

    A

    OK (When troubleshooting according to Problem Symptoms Table)

    B

    NG

    C
    A

    REPLACE AIR CONDITIONING CONTROL ASSEMBLY

    Click here

    B

    PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

    Click hereClick hereClick here

    C

    REPLACE NO. 1 COOLER THERMISTOR

    Click here