WARNING: This page is about a different car, the 2003 GMC Sierra and 2003 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: DTC P0172 & P0175: Fuel Trim System Rich - Bank 1 & 2 (Steps 1-6)
Courtesy of GENERAL MOTORS CORP.
Fig 2: DTC P0172 & P0175: Fuel Trim System Rich - Bank 1 & 2 (Steps 7 & 8)