P0172 - Where to start w/ diagnosis? 2008 Impala 3.5

Birdie2000

Birdie2000

Club Member
Been getting a P0172 "System too rich - bank 1" code for a few months now. It sporadically would go away and didn't really cause much problem so I didn't worry about it too much. I saw reports that it was possibly the computer calculating the alcohol content in the fuel incorrectly, but of course you need a Tech2 or other advanced scan tool to correct this which means an instant $100+ just to see if that is the issue.

Lately, the car has been having trouble starting because it seems the fuel mixture must be wrong during start up. The car runs fine otherwise and fuel mileage hasn't changed significantly.

This code seems to have 500 potential causes. I'm very hesitant to take it to a shop because I don't know of any that have been vouched for to spend the effort fully diagnosing the issue before replacing parts. I really don't want to just throw parts at it, but it's even worse if I'm paying a shop to do so instead of just doing it myself.

So, for a DIYer, what steps should I take to try and identify where my problem lies? I plan to try cleaning the MAF, and I have a bluetooth OBDII adapter and Torque/ScanmasterELM software if there are any values that I could monitor for clues.

Also, if anyone happens to know of a mechanic/shop who they can vouch won't take me on a wild goose chase in diagnosing this I'd be open to taking it somewhere.
 
First, clear your codes. Then if you are pretty certain it's a fuel mixture reading error, try locating the sensor. Should be by passenger front before wheel. look for a sensor with integrated fuel lines. Tap the sensor with a rubber mallet and see if the car changes drive-ability.
 
Codes have been cleared on a near daily basis. For my year it isn't a sensor, it's a calculation. Only way to do that is to reset fuel trims which supposedly requires an advanced scanner such as a tech 2.

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Clearing codes and leaving battery disconnected over an hour should make the FT's zero out. Im not 100% on that.
 
Thanks Larry, I might just take you up on that if I get the chance to head out that way.

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What have you looked at so far other than codes? Have you checked the system for any potential vacuum leaks that create a fuel trim fault?
 
I've looked at the easily visible lines but haven't probed too deeply yet.

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