Washed my "95 Blazer with the 4.3 engine and drove it a couple of miles to dry it off, about a mile into it, the service engine soon light came on. Drove it a couple of days and tried to read the fault codes with my reader which didn't work. Stopped by O'Reillys and they informed me that the O2 sensor was bad and offered to sell me one. Went home and got the one out of my part donor Blazer and installed it. Used but less than 5k miles on it. Drove it a week, about 200 miles and the light was still on. This time went to Auto Zone who said bank1 knock sensor is bad, went to NAPA who said the same thing. Got a knock sensor from Rock Auto. Old one was sort of sketchy, wire all twisted up.
New sensor installed and it does run better but the light is still on. Stopped by the local racer who put an old scanner on it, his new one wouldn't work at all, no codes recorded and he cleared the fault registry. Light was off for a couple of days and it came back. Not showing any faults, runs good but the light is on.

Any thoughts or ideas? Other than removing the bulb that is.

 

I suggest You visit the local guy again and ask for clearing the fault registry over again. If the light goes off, that would mean there is not likely a wiring or electrical problem, but indeed there is a faulty condition somewhere. The further question is how to list the code...

 

Well, we can clear it, might stay off for a day or maybe more or less. When it comes back, not if, there is no code stored......... No idea what it is.