B1242

Component Location






General Description

The Evaporator sensor located on heater unit detects the core temperature. It is a negative type thermistor whose resistance is inversely proportional to temperature. Evaporator sensor transforms measured temperature into voltage value and delivers it to A/C ECU. when core temperature is blow threshold value, A/C ECU interrupts compressor relay power, in order to prevent evaporator freezing by excessive cooling.

DTC Description

Air conditioner Control Module sets DTC B1242 if Evaporator 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 "Evaporator sensor" parameter on scantool.






Fig 1) Parameter of "Evaporator Sensor" will be fixed at -2°C(28.4°F), if there is any fault in Evaporator Sensor.
4. Is the Evaporator 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 Evaporator sensor and A/C control unit main harness connector.
3. Ignition "ON".
4. Measure voltage between Signal(F/B) terminal of Evaporator 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 Evaporator sensor and A/C control unit main harness connector.
3. Measure resistance between Signal(+) terminal of Evaporator 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 Evaporator sensor and A/C control unit main harness connector.
3. Measure resistance between ground terminal of Evaporator 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 Incar temp.sensor
1. Ignition "OFF".
2. Disconnect Evaporator sensor and Connect A/C control unit main harness connector.
3. Measure resistance between Signal(+) terminal of Evaporator sensor harness connector and Sensor ground harness connector.(Component side)

Specification :Refer the specifications in fig.1

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






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






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