3.
Monitor the "Driver Air Mix Potentiometer" Parameter on the Scantool while operating temp. switch.
Temperature control actuator located at heater unit, regulates the temperature by the procedure as follows. Signal from control unit adjusts position of temp. door by operating temp. motor and then temperature will be regulated by the hot/cold air ratio decided by position of temp. door.
The A/C controller sets DTC B1245 if there is an open circuit or poor connection in the air mix potentiometer.
Item | Detecting Condition | Possible cause |
DTC Strategy | ● Voltage check | ● Poor connection of connected part ● Open circuit in harness ● Short circuit in harness ● Faulty driver Air Mix potentiometer |
Threshold value | ● ＜ 0.1V | |
Detecting time | ● 0.3 sec | |
FAIL SAFE | ● If temperature setting 17~24.5°C(63~76°F) fix at max. cooling position. ● If temperature setting 25~32°C(77~90°F) fix at max. heating position. |
Connect scantool to Data Link Connector(DLC).
Engine "ON"
Monitor the "Driver Air Mix Potentiometer" Parameter on the Scantool while operating temp. switch.
Are the DTC B1245 present and is parameter of "Driver Air Mix Potentiometer" fixed?
※ Parameter of "Driver Air Mix Potentiometer" will be fixed at 100%(or any value above 90%), or 0% (or any value below 10%), if there is any fault in Driver Air Mix potentiometer.
Go to "Inspection" procedure.
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.
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.
Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage.
Has a problem been found?
Repair as necessary and go to "Verification of Vehicle Repair" procedure.
Go to "Signal circuit inspection" procedure.
Check for open in harness.
Ignition "OFF"
Disconnect Driver Air Mix potentiometer.
Measure resistance between terminal "6" of Driver Air Mix Potentiometer and terminal "18" of A/C control unit.
Specification : Approx. 0 Ω
Is the measured resistance within specifications?
Go to "Check for short to ground in harness" procedure.
Check for open in signal harness. Repair as necessary and go to "Verification of Vehicle Repair" procedure.
Check for short to ground in harness.
Ignition "OFF"
Disconnect Driver Air Mix potentiometer.
Measure resistance between terminal "6" of Driver Air Mix Potentiometer and chassis ground.
Specification : Approx. ∞ Ω
Is the measured resistance within specifications?
Go to "Power circuit Inspection" procedure.
Check for short to ground in signal harness. Repair as necessary and go to "Verification of Vehicle Repair" procedure.
Check for short or open in harness.
Ignition "ON"
Connect Driver Air Mix Potentiometer.
Measure voltage between terminal "7" of Driver Air Mix Potentiometer and chassis ground.
Specification : Approx. 5V
Is the measured voltage within specifications?
Go to "Component inspection" procedure.
Check for short or open in power harness. Repair as necessary and go to "Verification of Vehicle Repair" procedure.
Check actuator motor.
Ignition "OFF"
Disconnect Driver Air Mix Potentiometer.
Verify that the temperature actuator operates to the hot position when connecting 12V to the terminal "3" and grounding terminal "4".
Verify that the temperature actuator operates to the cool position when the connections are reversed.
Does the actuator work properly?
Go to "Check potentiometer" procedure.
Substitute with a known-good actuator and check for proper operation. If the problem is corrected, replace actuator and then go to "Verification of Vehicle Repair" procedure.
Check potentiometer
Ignition "ON"
Connect Driver Air Mix potentiometer.
Measure voltage between terminal "6" and "7" of Driver Air Mix potentiometer while operating the temp. switch.
Specification : Refer the specifications in fig 3)
Door position | Voltage (3-4) | Error detecting |
MAX. Cooling | 0.3 ± 0.15V | Low voltage : 0.08V or less |
MAX. Heating | 4.7 ± 0.15V | High voltage : 4.9V or more |
Is the measured voltage within specifications in fig3?
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.
Substitute with a known-good actuator and check for proper operation. If the problem is corrected, replace actuator and then go to "Verification of Vehicle Repair" procedure.
After a repair, it is essential to verify that the fault has been corrected.
Connect scantool and select "Diagnostic Trouble Codes(DTCs)" mode and then clear DTC.
Operate the vehicle and monitor the DTC on the scantool.
Are any DTCs present?
Go to the applicable troubleshooting procedure.
System is performing to specification at this time.
