Exhaust System: Hardware
WARNING: This page does not describe the selected car, but rather 31 other vehicles, including the 2003 Mercury Sable, 2003 Mercury Mountaineer, 2003 Mercury Marauder, 2003 Mercury Grand Marquis, and 2003 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.
The downstream HO2S may be located after light off catalyst or underbody catalyst. Underbody catalyst may be in-line with light off catalyst, or underbody catalyst may be common to 2 light off catalysts, forming a "Y" pipe configuration.