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33 Pin 7 Not Grounded at Diagnostic Monitor

Here is another explanation from Ford Trucks:

A code 33 is a hard code for the driver's side seat belt pretensioner. Here's a description of the code:

Normal Operation
The safety belt pre-tensioners are activated by the restraints control module (RCM) to remove excess slack from the safety belt webbing when an impact exceeding preprogrammed limits is detected.

The RCM checks all of the safety belt pretensioners for faults. If the RCM detects one of the following faults on any of the safety belt pretensioner circuits, it will store diagnostic trouble code (DTC) B2292 in memory and flash, depending on the fault indicator, either lamp fault code (LFC) 33 or 34 depending on the fault (or higher priority code, if one exists,) on the airbag indicator.

Fault Conditions
The RCM monitors for the following fault conditions:

* Low resistance
* High resistance or circuit open
* Circuit short to voltage
* Circuit short to ground

Possible Causes
A safety belt pre-tensioner fault can be caused by:

* damaged wiring, terminals or connectors.
* a faulted pretensioner.
* a faulted RCM.:

I would recommend checking the connector for the belt pretensioner on the driver's side.
 I've seen problems with corrosion on the terminals in this connector causing the light to go on.

Here is a link to a TSB that says it might be a loose connector:

http://www.explorerforum.com/forums//archive/index.php/t-150784.html