Which Denso sensor for code P0171 Too Lean. Before or after Cat?

Question

On my 2002 Toyota Camry which Denso sensor for code P0171 Too Lean. Before or after Cat?

Answer 1

Hi there,

This code can be a result of the rear o2 sensor not functioning properly, but more commonly is the front O2 sensor. This is as long as the fuel pressure is good, there aren't any intake leaks and the exhaust manifold isn't cracked.

All of these can result in the lean code.