B1234

B1234

Component Location:

General Description
The incar temperature sensor joined to Humidity sensor as one body is located at heater control unit. It contains a thermistor which measures the temperature of the inside. The signal,decided by the resistance value which changes in accordance with perceived inside temperature, is delivered to heater control unit. According to this signal, the control unit regulates incar temperature to intended value.

DTC Description
The ECM sets DTC B1234 if there is an open circuit in incar temp sensor signal harness or the measured voltage value of the sensor is more than the threshold value (4.9 V)

DTC Detecting Condition:

Schematic Diagram:

Signal Waveform:

Monitor Scantool Data
1. Connect scantool to Data Link Connector (DLC).
2. Engine "ON".
3. Monitor the "INCAR TEMP.SENSOR" Parameter on the Scantool.






4. Are the DTC B1234 present and is parameter of "INCAR TEMP.SENSOR" fixed?
- Parameter of "INCAR TEMP.SENSOR" will be fixed at 77 °F, if there is any fault in INCAR SENSOR

YES
a. Go to "Inspection & Repair" procedure.

No
a. Fault is intermittent caused by poor contact in the sensor's and/or A/C control unit's connector or was repaired and A/C control unit 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
a. Repair as necessary and go to "Verification Vehicle Repair" procedure.

No
a. Go to "W/Harness Inspection" procedure.

Signal Circuit Inspection
1. Check for open in harness
1. Ignition "OFF".
2. Disconnect incar temp.sensor.
3. Measure resistance between terminal "4" of incar temp.sensor and terminal "8" of A/C Control Unit.

Specification : Approx. 0 ohm






4. Is the measured resistance within specifications?

YES
a. Go to "Ground circuit Inspection" procedure.

No
a. Check for open in harness. Repair as necessary and go to "Verification of Vehicle Repair" procedure.

Ground Circuit inspection
1. Check for open in ground harness
1. Ignition "OFF".
2. Disconnect incar temp.sensor.
3. Measure resistance between terminal "2" of incar temp.sensor and terminal "16" of A/C Control Unit.

Specification : Approx. 0 ohm






4. Is the measured resistance within specifications?

YES
a. Go to "Component Inspection" procedure.

No
a. Check for open in ground harness. Repair as necessary and go to "Verification of Vehicle Repair" procedure.

Component Inspection
1. Check Incar Temp. sensor
1. Ignition "OFF".
2. Disconnect incar sensor.
3. Measure resistance between terminal "4" and "2" of incar sensor.

Specification : Refer the specifications in fig 3)









4. Is the measured resistance within specifications in fig 3)? (tolerance limits ± 3%)

YES
a. 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
a. Substitute with a known-good incar sensor and check for proper operation. If the problem is corrected, replace incar sensor 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
a. Go to the applicable troubleshooting procedure.

No
a. System is performing to specification at this time.