B1237

COMPONENT LOCATION





GENERAL DESCRIPTION

The ambient temperature senor located at the center stay of the condenser, detects ambient air temperature. It is a negative type thermistor whose resistance is inversely proportional to temperature. Its output is used for discharge temperature sensor, sensor fail-safe, temperature regulation door lock, blower motor level control, mix mode control and in-car humidity control.

DTC DESCRIPTION

The A/C controller sets DTC B1237 if there is a short circuit in ambient temp. sensor signal harness or the measured resistance value of sensor is less than threshold value(about 7.48kOhms)

DTC DETECTING CONDITION





SPECIFICATION





MONITOR SCANTOOL DATA

1. Connect scantool to data link connector(DLC).
2. Engine "ON"
3. Monitor the "AMBIENT TEMP. SENSOR" Parameter on the Scantool.
** Parameter of "AMBIENT TEMP. SENSOR" will be fixed at 20°C, if there is any fault in AMBIENT TEMP. SENSOR.




4. Are the DTC B1237 present and is parameter of "AMBIENT TEMP. SENSOR" fixed?
YES
Go to "Inspection" procedure.
NO
Fault is intermittent caused by poor contact in the sensor's and/or A/C controller's connector or was repaired and A/C controller memory was not cleared. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and then go to "Verification of Vehicle Repair" procedure.

TERMINAL AND 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?
YES
Repair as necessary and go to "Verification of Vehicle Repair" procedure.
NO
Go to "Signal circuit inspection" procedure.

SIGNAL CIRCUIT INSPECTION

1. Check for short to ground in harness.
(1) Ignition "OFF"
(2) Disconnect ambient temp. sensor.
(3) Measure resistance between terminal "1" of ambient temp. sensor and chassis ground.

Specification : Approx. InfinityOhms





(4) Is the measured resistance within specifications?
YES
Go to "Component Inspection" procedure.
NO
Check for short to ground in harness. Repair as necessary and go to "Verification of Vehicle Repair" procedure.

COMPONENT INSPECTION

1. Check Ambient temp. sensor.
(1) Ignition "OFF"
(2) Disconnect ambient temp. sensor.
(3) Measure resistance between terminal "1" and "2" of ambient temp. sensor.

Specification : Refer the specifications in fig 3.









(4) Is the measured resistance within specifications in fig3? (tolerance limits ±3%)
YES
Go to "Check A/C Control Unit" procedure.
NO
Substitute with a known-good ambient temp. sensor and check for proper operation.
If the problem is corrected, replace ambient temp. sensor and then go to "Verification of Vehicle Repair" procedure.
2. Check A/C Control Unit
(1) Engine "ON"
(2) Disconnect ambient temp. sensor.
(3) Measure voltage between terminal "3" of A/C Control Unit and chassis ground.

Specification : Approx. 5V





(4) Is the measured voltage within specifications?
YES
Check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and then go to "Verification of Vehicle Repair" procedure.
NO
Substitute with a known-good A/C Control Unit and check for proper operation.
If the problem is corrected, replace A/C Control Unit and then go to "Verification of Vehicle Repair" procedure.

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?
YES
Go to the applicable troubleshooting procedure.
NO
System is performing to specification at this time.