The E2 error indicates a Sleep Number® mattress has taken longer than the standard amount of time to inflate from one Sleep Number® setting to the next. The most common cause is a loose connection between the Firmness Control™ base and the air chambers.
To remedy this, verify the hoses are free of kinks, and then gently tug each of the hose connections to check that all connections are secure. Hoses snap into place when connected properly. Depending on which bed you own the hose connections will be either at the head of the bed or on each side of the bed.