Diagnostic Aids

WARNING: This page is about a different car, the 2019 GMC Savana 3500, 2019 GMC Savana 2500, 2019 Chevrolet Express 3500, and 2019 Chevrolet Express 2500. However, it is still accessible from the selected car via links, so may be relevant.

A faulty fuel feed front pipe check valve may cause a rattle, tick, knock, or buzz noise. The noise may be more pronounced at idle, approximately 600-800 RPM.
An erratic low side fuel pressure reading may be caused by a faulty fuel feed front pipe check valve.
Observe the Misfire Counters or perform the Fuel Injector Diagnosis to help identify a leaking fuel injector.