AIR CONDITIONING SYSTEM(for Automatic Air Conditioning System) Ambient Temperature Sensor Circuit

DTC Code DTC Name
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.

WIRING DIAGRAM

E270948E09

PROCEDURE

  1. INSPECT THERMISTOR ASSEMBLY

    1. E268073C05

      *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

      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:

      • 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 here

    OK

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

    1. Disconnect the E12 combination meter assembly connector.

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

      Standard Resistance

      Tester Connection

      Condition

      Specified Condition

      E12-17 (TX1+) - A50-1

      Always

      Below 1 Ω

      E12-18 (TX1-) - A50-2

      Always

      Below 1 Ω

      E12-17 (TX1+) - Body ground

      Always

      10 kΩ or higher

      E12-18 (TX1-) - Body ground

      Always

      10 kΩ or higher

    Result

    Proceed to

    OK

    NG
    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  3. REPLACE COMBINATION METER ASSEMBLY

    1. Replace the combination meter assembly.

      Click 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.

      OK

      Malfunction disappears.

    Result

    Proceed to

    OK

    NG
    OK

    END (COMBINATION METER ASSEMBLY WAS DEFECTIVE)

    NG

    PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

    Click hereClick hereClick here