Buick Lesabre showing code p0171

[longtimecoug]

02 lesabre showing code p0171, after resetting the code the light stays out until I shut it off and restart. I have replaced the fuel filter and also the MAP sensor, which fell apart in my hands as I was trying to get to the PCV valve, also replaced. the MAF sensor was replaced previously, after which the p0171 code started showing up, what else can i try?

[carriedi]

p0171 is just telling you where to start looking. How is your oxygen sensor working? What does your fuel trims tell you? Check your freeze frame to let you know what is happening when the code sets.

If the MAF sensor was replaced and then you started to have the code show up, maybe your MAF is not reading correctly. Why did you replace the MAF?

[longtimecoug]

I replaced the MAF because it was giving a code, I forget which one now but it wasn't functioning properly I tried cleaning it first but it made no difference so I replaced it, I am unfamiliar with freeze frame and fuel trim

[carriedi]

freeze frame is the data information that the computer saves when a hard code is set. It is part of the OBD2 diagnostics. it will tell you what was happening when the code was set.

Fuel trim is what the computer is setting the fuel parameter to, so that the oxygen sensor will read within spec. It has a short term value and a long term value. It tells you if the computer is adding fuel or subtracting fuel to compensate for problem according to the oxygen readings.

If your MAF reading is low your computer will send a low amount of fuel. and normally that's fine. But if your MAF is low because it is inaccurate the computer will send a low amount of fuel and your oxygen sensor will see too much oxygen in the exhaust. (a lean condition). The fuel trim will go up to compensate. If fuel trim has to go up too much you will set the code for lean condition. It could be MAF signal too low. Vacuum leak in the system somewhere. Bad oxygen sensor. bad or poor injector output. Low fuel pressure or volume. misfire. even a bad PCM.

looking at the data stream graphs with a scanner while you're driving will help narrow what to look for.

so, you had a code for the MAF and you replaced it. Then you started to have the P0171 codes come up? If it happened just like that maybe your MAF isn't working correctly.

[longtimecoug]

I'm going to put the old MAF back in and see what happens with the codes, the one I put in was a cheap part I got on amazon

[longtimecoug]

replaced MAF with the old one and now no codes, I drove quite a while turned engine on and off several times and no codes came up, hopefully the problem has been solved

[longtimecoug]

light is back on, code p0102, but not p0171

[carriedi]

maf frequency at idle should be around 2000. If your maf has 1200 hz or less for 12 seconds your car will turn on the check engine light the second consecutive time it happens. (for code P0102) Check for a vacuum leak. The results you have from the two maf sensors indicate you may have a vacuum leak throwing the readings out of whack.

[Johnnytime]

My 2001 Buick Regal w/ 3.8L 3800 Series 2 required OEM or original equiptment MAF Sensor. Delphi is good.
Remanufactured or New other brands will give you the P0171 code after changing MAF to cure p0102 !

This is based on my own experience and frustration with P0171.