B1200
B1200Component Location:
General Description
Humidity sensor located at heater control unit detects in-car humidity for in-car humidity control. Humidity sensor and incar sensor are joined as one body. Humidity sensor transforms measured humidity into frequency value and delivers it to A/C Control unit. If ambient air temperature or in-car humidity is in a specified range that can makes frost on the window glass, A/C will be activated to control in-car humidity to prevent frost on the window glass.
DTC Description
The ECM sets DTC B1200 if there is an open circuit or poor connection of connected part in humidity sensor signal harness.
DTC Detecting Condition:
Schematic Diagram:
Signal Waveform:
Monitor Scantool Data
1. Connect scantool to Data Link Connector (DLC).
2. Engine "ON".
3. Monitor the "Humidity Sensor" Parameter on the Scantool. While drying the humidity sensor with the implement such as hair drier.
4. Are the DTC B1200 present and is parameter of "Humidity Sensor" fixed?
- Parameter of "Humidity Sensor" will be fixed at 10%, if there is any fault in Humidity 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 Humidity Sensor.
3. Measure resistance between terminal "3" of Humidity Sensor and terminal "7" of A/C Control Unit.
Specification : Approx. 0 ohm
4. Is the measured resistance within specifications?
YES
a. Go to "power circuit Inspection" procedure.
No
a. Check for open in harness. Repair as necessary and go to "Verification of Vehicle Repair" procedure.
Power Supply Circuit Inspection
1. Check for open in harness.
1. Ignition "ON".
2. Connect Humidity sensor.
3. Measure resistance between terminal "5" of Humidity Sensor and terminal "1" of A/C Control Unit
Specification : Approx. 0 ohm
4. Is the measured resistance within specifications?
YES
a. Go to "Check for short in harness" procedure.
No
a. Check for open in harness. Repair as necessary and go to "Verification of Vehicle Repair" procedure.
2. Check for short in harness.
1. Ignition "ON".
2. Connect Humidity sensor.
3. Measure resistance between terminal "5" of Humidity Sensor and chassis ground.
Specification : Approx. Infinite ohms
4. Is the measured resistance within specifications?
YES
a. Go to "Ground circuit Inspection" procedure.
No
a. Check for short 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 Humidity Sensor.
3. Measure resistance between terminal "2" of Humidity 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 A/C Control Unit
1. Engine "ON".
2. Disconnect Humidity Sensor.
3. Measure voltage value between terminal "1" of A/C control unit and chassis ground.
Specification : 5 V
4. Is the measured voltage within specifications?
YES
a. Go to "Check Humidity Sensor" procedure.
No
a. 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.
2. Check Humidity Sensor
1. Engine "ON".
2. Connect Humidity Sensor.
3. Measure Frequency between terminal "3" and "2" of Humidity sensor while increasing humidity.
Specification : Refer the specifications in fig 5)
4. Is the measured frequency within specifications in fig 5)? (tolerance limits ± 5%)
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 Humidity sensor and check for proper operation. If the problem is corrected, replace Humidity 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.