'00 Buick Century p0172 error

Hello all,
I have a '00 Buick Century Limited and the service engine light has been coming on. I checked it with an ODB-II and it read P0172. Now, I
have changed the Oxygen Sensor, however it is still giving the same error. I ran a bottle of Injector Cleaner through and the light still came back on.
I haven't checked the MAF with a voltmeter yet, but I will and I doubt that this is is. What else could it be? A bad injector? I'm running out of ideas so any help is greatly appreciated.
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Why would the first thing you do is replace the oxygen sensor for a P0172?
Start with the cheap stuff: change your air filter and clean your throttle body. Look for a blockage in the intake. Check the vacuum line going to the fuel pressure regulator for fuel, if there is fuel in the line, replace fuel pressure regulator. Check fuel pressure. Run injector cleaner through the system (which I see you have done).
If you have a scan tool (not a code reader), check for proper operation of the MAF, IAC motor and TP sensor. At this point, I would take it to a good mechanic and let them do a quick diagnosis, they should be able to find the problem quite quickly. Then you can take it and replace the offending components.
Steve
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Well, I thought that the O2 sensor might have been bad and it was one of the listed possible causes. No big deal. One other clue that may narrow it down is that the Service Engine light only comes on when the gas tank gets lower... on a full tank the light doesn't come on. Does this help at all?
I don't have a scan tool unfortunately, the best I can do is to use a voltmeter on the MAF harness to check for 12v.
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Oxygen sensor IS one of the possible causes, but it's down on the list. Did you check the other things I mentioned? If so, I would seriously consider taking it to a mechanic, he'll tell you what's wrong. Most likely something any competent mechanic can diagnose in well under an hour.
Steve

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