Note On INTERMITTENTS
If an intermittent Code B440 is being set, check Code B440 snap data BD23 display. If BD23 value was zero percent, check for an intermittent open in circuit No. 736. If BD23 value was 100 percent, check for an intermittent open in circuit No. 733 or 705. If BD23 value 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 at least 2 minutes in each mode to see if code sets.