Re: The check engine light that no one can turn off.
ok, lets start by saying i am not familiar with a 00 sable, i am a GM tech and i sift around to different forums looking at types of problems other vehicle makers have. A P0171 is a Fuel trim system lean code. Ok, your o2 sensors would read bad with a lean code, not necessarily meaning they are bad, but getting a bad reading. the tech should monitor 02 mV readings to deem this true.( you will want a good rich to lean sweep on your Sensor before the cat, and a more steady signal around 500 mV after cat.) Now, what would make it lean, a vaccum leak (do the carb cleaner trick, take a can and spray any vaccum lines, (including vaccum lines to EVAP) fittings and around the upper intake observing any change in idle) also check lines for kinks, incorrect MAF( MAss Air Flow) reading (from contamination or being restricted, check that out make sure it is free of debris). A fuel pressure test should also be done, not just at priming, but observe bleed down time and actually tape the guage to the windshiled and drive the car with the guage on, and see if any certain driving condition gives a bad reading. A diagnostic tool would be prime, as you would also want to check IAC actual and desired counts. I hope this get you off on a start if you want to try to diagnose this yorself, good luck to you