I'm replacing my front O2 sensors. I'm hoping that will allow my EFIE's work better.
My question is about the rear ones. Could old rear O2 sensors effect performance on these 2 vehicles. (no codes or lights) 2001 GMC 3500, and 1994 Nissan quest.
The GMC has 2 options on front O2 sensors. Over 8500 lbs and under 8500 LBS, does anyone know the differance? Does the under look for a leaner exhaust?