Diagnosing P0172

[MickeyD]

Morning all,

I apologize if this is a question that's been addressed before.

This morning while driving, my truck threw a P0172 code, but not a P0175. I've done some reading online, and I see there's a lot of different potential causes. I'd like to narrow it down slightly with some help.

My air filter is clean and clear, but I have not checked or done anything with the MAF sensor. I'm not sure what's involved with trying to clean it, or if it's better to just replace. Alternatively, I don't know what the fuel pressure is doing, nor have I done anything with the injectors. I also know that an O2 sensor can be at fault.

For reference, the truck has 156k miles on it, bought it with 128k, but I don't know much about the history beforehand. It runs okay, but it idles rough from what I'm fairly certain are original plugs. It's been on my list to replace them, but I hesitate cause I'm worried about snapping something off then being out of commission for a bit. I should probably just bite the bullet and have the dealer replace them.

Because I don't have the P0175 code, I'm thinking it's not something with the MAF sensor or the fuel pump, as these would affect both banks. So, I'm thinking it might be the O2 sensor for that bank, a clogged injector on that side, or possibly a plug on that side. Because the quality of how the engine runs is unchanged (not obviously missing), my thought is the O2 sensor.

Before I buy parts or start pulling injectors, though, I welcome any advice or guidance you guys can provide! Thanks in advance!

 

[OR VietVet]

IMO, if those plugs are original, you said you did not know, you need to change them and the wires with GM parts and not aftermarket components. Also, get MAF/MAP sensor cleaner and follow the instructions. Watch a few you tube videos for the procedures or have the dealer do it all if you do not have the mechanical abilities. If you have that old of a plug(s) then you are helping dump unburned fuel down the exhaust. It is time for all 4 oxygen sensors too. They do not last forever. Believe it or not, all of this, including sensors, is considered maintenance.

Also, if you love the dealer, fine, go there. Otherwise I would find a reputable independent shop and check for ASE certifications and reviews and also word of mouth and see if they will allow you supplying parts as long as they are high quality GM parts, that you can still buy cheaper at RA and Amazon and other sources.

Personally, I would live in fear if the place I took my rig to was always a dealer.

 

[wsteele]

Since you are only getting the rich condition on Bank 1, my guess would be the upstream O2 sensor (the one in front of the cat) on the driver's side. Before buying parts, I would see if I could look at the live data on the scanner and see if that O2 sensor is switching properly. If it is largely flat line then it is a simple remove and replace. If it seems to be switching properly (going up and down in values), then I would do the MAF clean procedure.

Definitely time for new plugs and wires, if they have never been replaced.

 

[Foggy]

As stated, MAINTENANCE is the key here...
Plugs, Wires, Clean MAF, Use Techron Concentrate in your fuel, Clean
the air intake system -before and after the filter.
Upstream O2 Sensors only last 100K at best.. They get very inefficient/inaccurate
after so many miles..
Downstream aren't as crucial.
Rich condition in your case is prob unburned fuel due to lack of maint
And once your plug gap grows, the coilpacks have a hard time sparking across the
greater gap leading to failed coilpacks

 

[donjetman]

MickeyD, is it consuming any oil? If so, install the updated driverside valve cover and a catch can if you haven't already done so.
Valve cover # 12642655 for 2009-2011
Valve cover # 12570427 for 2007-2008