1998 Chevrolet Tracker P1400 Error: EGR Flow Fault Diagnosis and Symptoms

Model: 1998 chevrolet tracker Fault Code: P1400 Posted: 2006-01-04 22:02

My wife's 1998 Chevrolet Tracker is displaying a P1400 diagnostic trouble code, indicating an EGR flow error. I'm trying to understand how the EGR system determines whether it's actively flowing or not. Does it rely on data from the oxygen (O2) sensor? Additionally, when I apply vacuum at idle, the engine stumbles. I installed a vacuum gauge and performed a test drive—during operation, the EGR line shows 2–5 psi of vacuum intermittently. Can anyone provide insight into what might be causing this issue or how to properly diagnose the EGR flow system?