Note On Intermittents
If an intermittent Code B440 is being set, check B440 snap data BD23 display. If it was zero percent, check for an intermittent open in circuit No. 736. If it was 100 percent, check for an intermittent open in circuit No. 733 or circuit No. 705. If it was 1-99 percent, check for binding door movement throughout range of door travel and check for a poor ground circuit No. 803. Manipulate related wiring while observing actual air mix door position (BD23 display) movement. If failure is induced, valve (door) position will either stop or jump to an extreme value (zero or 100 percent). This will assist in isolating location of malfunction.
Exit diagnostics and select maximum heat (90°F) and maximum cool (60°F) using normal HVAC controls, waiting a minimum of 2 minutes in each mode to see if code sets.