B1238

Component Location






General Description

It is a negative type thermistor whose resistance is inversely proportional to temperature. Its output is used for sensor fail-safe, temperature regulation door lock, blower motor level control, mix mode control.

DTC Description

Air conditioner Control Module sets DTC B1238 if Ambient sensor has been detected over 4.9V for 4sec.

DTC Detecting Condition






Specification

** Resistance value of incar temp sensor as a function of temperature.






Diagnostic Circuit Diagram






Monitor Scantool Data

1. Connect scantool with diagnostic connector.
2. Warm up the engine to normal engine temperature after engine starts.
3. Select and monitor "Ambient Air Temperature sensor" parameter.






Fig 1) Parameter of "Ambient Sensor" will be fixed at 20°C(68°F), if there is any fault in Ambient Sensor.
4. Is the ambient sensor normal ?






Terminal & Connector Inspection

1. Many malfunctions in the electrical system are caused by poor harness and terminals. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.
2. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration,or damage.
3. Has a problem been found?






Signal Circuit Inspection

Check short to battery in harness
1. Ignition "OFF".
2. Disconnect ambient sensor and A/C control unit main harness connector.
3. Ignition "ON".
4. Measure voltage between Signal(F/B) terminal of ambient sensor harness connector and chassis ground.

Specification :0V

5. Is the measured voltage within specification?






Check for open in harness
1. Ignition "OFF".
2. Disconnect ambient sensor and A/C control unit main harness connector.
3. Measure resistance between Signal(+) terminal of ambient sensor harness connector and Signal(+) terminal of A/C-ECU harness connector.

Specification :1Ohms below

4. Is the measured resistance within specification?






Ground Circuit Inspection

Check for open in harness
1. Ignition "OFF".
2. Disconnect ambient sensor and A/C control unit main harness connector.
3. Measure resistance between ground terminal of ambient sensor harness connector and ground terminal of A/C-ECU harness connector.

Specification :1Ohms below

4. Is the measured resistance within specification?






Component Inspection

Check Ambient sensor
1. Ignition "OFF".
2. Disconnect ambient sensor and Connect A/C control unit main harness connector.
3. Measure resistance between Signal(+) terminal of ambient sensor harness connector and Sensor ground harness connector.(Component side)

Specification :Refer the specifications in fig.1

FIG.1) ** Specifications : Resistance value of ambient sensor as a function of temperature.






4. Is "resistance" display near the specified value?





Check A/C-ECU
1. Ignition "OFF".
2. Disconnect Ambient Temp. sensor (+) and Connect A/C control unit main harness connector.
3. Ignition "ON"(ENGINE "OFF").
4. Measure voltage between Signal(+) terminal of Ambient Temp. sensor (+) harness connector and chassis ground.(Component side)

Specification :Approx. 5V

5. Is "voltage" display near the specified value?






Verification of Vehicle Repair

After a repair, it is essential to verify that the fault has been corrected.
1. Connect scantool and select "Diagnostic Trouble Codes(DTCs)" mode and then clear DTC.
2. Operate the vehicle and monitor the DTC on the scantool.
3. Are any DTCs present?