DTC 54 & 55: Passenger-Side Air Bag Module
WARNING: This page is about a different car, the 2003 Mitsubishi Outlander. However, it is still accessible from the selected car via links, so may be relevant.
If DTC 54 or 55 is present, replace SRS ECU. See SRS ELECTRONIC CONTROL UNIT (SRS ECU) under REMOVAL & INSTALLATION.