Code B440 - Air Mix Door Problem: Notes
NOTE:
Following procedure is designed to account for intermittent codes. If no malfunction is uncovered using this procedure,it will indicate that DFI system is okay at this time.
Code "B440" is set by BCM if it is unable to move air mix door. The BCM requests door to move over data circuit (circuit No. 800) to programmer. The programmer then supplies voltage to DC motor which drives air mix door. The BCM monitors feedback pot on DC motor which varies between zero (0) and 5 volts, depending on its position.
If door is requested to move, but feedback voltage does not change, BCM checks to see if door has reached its mechanical limit of travel. If door is not at its mechanical limit of travel, BCM stores code to indicate that door is not responding to its commands.
- BCM data value "BD23" displays actual air-mixture door position. The normal range is between 1% and 99%. BCM override value "BS01" is for program number.
- Checks to see if fault could be due to 5-volt reference and ground circuit or sensor circuit.
- Checks to see if the fault is due to programmer or sensor circuit.
- Check to see if fault is due to circuit or BCM.
- This step checks to see if open circuit reading is due to circuit No. 736 or circuit No. 705.