Ive got a 92 f150 with a 5.8. Code 172 sets for "ego not switching lean exhaust sensor one" or bank one, something like that. Ive searched for vacuum leaks, cant find any. Fuel pressure is at 40lbs, i think the spec is 35-45 KOEO. Im able to force the 02 reading anywhere from .1-.8 volts so the 02 sensor is functioning properly. Any ideas? plan to put a scanner on it tomorrow to check ect sensor and so on.

 

An exhaust leak close to the O2 sensor will also give a lead reading. Could be a gasket, cracked manifold, or a hole rusted in the exhaust.