Orifice Tube Assembly
WARNING: This page does not describe the selected car, but rather 32 other vehicles, including the 2002 Mercury Sable, 2002 Mercury Mountaineer, 2002 Mercury Grand Marquis, 2002 Mercury Cougar, and 2002 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.
Orifice tube assembly is the section of tubing connecting exhaust system to intake manifold. Orifice tube provides a flow path for exhaust gas to intake manifold. The orifice tube contains a metering orifice and 2 pressure pick-up tubes. See Fig 1. The metering orifice creates a measurable pressure drop across it as EGR valve opens and closes. The pressure differential across the orifice is picked up by DPFE EGR sensor which provides feedback to PCM.