I've never heard of O2 sensors failing with out a code.
I've dealt with failed oxygen sensors without popping a code, it doesn't happen all the time been in this business too long to know better-here's my grocery list that will caused a severe hesistation. If you're unsatisfied request for refund as stated-
Fuel injectors dirty/sticking.
Mass airflow sensor/Airflow meter.
Throttle position sensor.
Crankshaft position sensor
Manifold absolute pressure sensor.
Fuel pressure regulator leaking or defective fuel pump.
False air leakage.
Foul/defective spark plugs.
Open spark plug wires.
Ignition coil/Coil packs defective.
Incorrect ignition timing.
Cap and rotor.
Note:If it doesn't apply disregard
Thursday, September 16th, 2010 AT 6:30 PM