2002 Infinity QX4: Does anyone have a clue as to why the Service Engine Light appeared 2 days after 3 emission sensors were replaced?
emissions sensors . . . I suppose you mean the oxygen sensors, correct?
I’m just guessing . . . but your car may have been misdiagnosed
By the way, please post the original codes . . . the ones that led you to have the sensors replaced
And get the codes read again . . . please post those codes, as well
No one can answer that question based on that amount of information.
What sensors were replaced? Why were they replaced? If there were error codes leading to the replacement, find out what they were and post them (e.g. “P0123”). If the engine light is now on (again?) then there are more codes (or the same codes). Find out what the codes are and post them. Note that codes don’t tell you that sensors are bad.
Include more info on vehicle - mileage, maintenance history.
Agree with @db4690 . I am of the opinion that the majority of O2 sensors and catalytic converters replaced on vehicles in this country is done needlessly.
Without knowing the codes that were/are present there are too many possibilities to even start guessing.
Perhaps it’s time for an oil change?
C’mon, man, give us something to work with here. What are the codes, what sensors were replaces, are there any symptoms, has the maintenance been kept up to date. Stuff like that.
In the old days, 1950’s through 1970’s, it would have been possible to venture a guess on something like this. Or you could just start replacing likely parts until the problem went away.
Todays cars are so complicated, the parts and labor costs so high, doing such a thing is somewhere between impossible and economically impractical. You’d likely run out of money replacing stuff before you found the problem. To aid in problem diagnoses in modern cars, the manufacturer installs sophisticated software into the car’s computer. You paid for this software so you might as well use it. Ask you mechanic to bring out the scan tool and run the car’s diagnostic software. That’s what you want to rely on as your first line of defense.