98 Ford Expedition OBD Code P0402: How to Diagnose and Fix EGR Valve and DPFE Sensor Issues

Model: 98 Ford Expedition Fault Code: P0402 Posted: 2005-03-15 11:01

My 1998 Ford Expedition has triggered the check engine light, and my friend, a mechanic, advised me to test the EGR valve. He suggested using a tube connected to the top of the valve and sucking on it while the engine is running—if the engine almost stalls, the EGR valve is likely functioning properly. Additionally, he mentioned checking the DPFE (Differential Pressure Feedback Emission) sensor, but I'm unsure how to tell if it's faulty. Can anyone provide clear guidance on identifying whether either component is malfunctioning? What are the common symptoms of a bad DPFE sensor or EGR valve in a 1998 Ford Expedition with OBD code P0402?