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Common cause of Code P0171?

27K views 18 replies 10 participants last post by  arogers260  
#1 ·
Getting Code P0171 (System Too Lean Bank 1) and would like to know the common cause.

FYI, also coding P0420 (Catalyst System Efficiency Below Threshold Bank 1).

Are these related in any way?

Thanks.
 
#3 ·
Getting Code P0171 (System Too Lean Bank 1) and would like to know the common cause.

FYI, also coding P0420 (Catalyst System Efficiency Below Threshold Bank 1).

Are these related in any way?

Another yes vote. Obviously fuel related, too lean & not burning efficiently enough. I am not a mechanic but I am assuming "bank" is one side of the engine. Left & Right Bank. How is the thing running?
 
#10 ·
ct essence...i am betting it is not the O2 sensor or anything to do with bank one. i bet your next codes that go with that will be P0161 and P0158 or something along those lines. i hate to say it bro, but the ECM may be going down hill. as you know if this is the case, you can get oen for $240ish and just have it flashed at your loacl dealership for @ $100 and be good to go. this is not going to hurt your car if you continue driving it like this if it is actually the ECM, but if it is actually the O2 sensor, then it could start to hurt your car in due time...but if you are mechanically inclined, shoot the wires from the ECM to the O2 sensor and see if they are good. if they are, then it is more than likely the ECM
 
#17 ·
So I've been having this same issue p0171 and 0174 as of me changing passenger side o2. I had the back two taken out of the equation and the cats gutted yet still the same code however I have heard a ton of different causes on this from mar, fuel pump, vacuum leak, too small of air filter and the scariest for me being I have a Maggie on mine is the intake manifold having a leak. Being as I had someone change my plugs and it got worse I'm going for the wires he probably broke then just pulling my aur filter off to see if that does anything. All that being said bank one is the passenger side right?
 
#18 ·
Ok so both banks showing code air filter has nothing to do with it. Chances are it got cold and that intake gasket with all the Maggie pressure and being froze from weather probably cracked it s.o.b. I'm sure I've just begun to curse it but still. I now have to either cheapie it spray and then jb weld or high heat cauk... Hehe high heat cauk. Or pull the whole thing off and replace it. Anyone know of better intake gaskets so this Dosnt happen again?
 
#19 ·
Typically lean codes are caused from too much air. Start with your air box to check they're aren't any gaps, especially the bottom corners. If this is not the issue then work your way down the troubleshooting line. I know my lean codes are the air box not sealing to the filter gasket in the bottom corners. EVERYTIME I've had a lean code the air box not sealing has been the problem.