Learn why lean trouble codes P0171 and P0174 often point to other engine problems instead of faulty oxygen sensors.

P0171 is a diagnostic trouble code that means the engine’s air-to-fuel mixture on Bank 1 is too lean, with too much air relative to the amount of fuel being delivered. The most common cause is a ...

Fault code PO171 usually indicates a lean air:fuel mixture entering the engine. As in there’s too much air and not enough fuel. This creates all sort of problems including poor running, but it could ...