I spoke with my contact at Lippert and this is what they sent me about the external sensor issue you have:
External sensor error means there is an issue with the rear leveling sensor. This will be located 2-3 foot behind the rearmost axle. There may be an access panel in the underbelly, or there may not. Typically this error is due to a bad connection to the sensor.
It is important that once the error code has been resolved, the user of the unit must manually retract all jacks completely... view full answer...