Can all three oxygen sensors be bad at one time without the check engine light coming on?

Answer 1

It is highly unlikely for all three sensors to go bad all at once .It would take a massive short circuit or something like that,at which point the engine would stop. If three 02 sensors are not functioning and you have no check engine light,the computer is bad and has lost it,s diagnostic ability.Again unlikely,the engine would run very poorly in a limp in mode. keep checking you dtc's and testing

________________________________________________________________

Just to add to this I have a question of my own. You said it would have to be like a major electrical overload. I'm having a problem in my standard truck now that began after I stalled out. It's gotten much worse now and a mechanic friend of mine says it sounds like 02 sensors. I know I'm going to sound like an idiot, but it had been awhile since I drove a standard and I came to a complete stop doing about 45 mph while in 4th gear without engaging the clutch. The truck almost committed suicide for lack of a better term. I had to replace several blown fuses and since then it's gotten harder to start after the vehicle is warm. Everything in the starter system seems to operate correctly it sparks up and turns over, but it just won't sustain ignition after trying to start without adequate cool down time - something about not having the appropriate fuel to Air Ratio.