P0171 code SS SC
 

Well I got a code on the Cobalt, its a P0171 running lean code. So first I changed the maf, it kept the light off for 50 miles. So then I go check my wires going to the maf, they all look good. So I disconnect the battery hoping to will keep it off for a other 50 miles, it came back with in 5 miles. I checked all my house clamps for the intake, everything looks fine. So anyone who got this code before, what was it? I have a spare ebay intake my uncle gave me, that I might slap on and see if my stock intake for some reason is giving me the code.

So if you have had the code before, what threw your code, and how did you get rid of it? Thanks for any help given. I need to DEQ my car real soon.

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Bumping it over and over wont do shit for a reply

ps. its a generic code generally cause by o2 not MAF.

Well do you have a idea that may help? Ive been looking over my wiring, and my intake, and for vac leaks. Im just wondering maybe someone else had the problem and it was a simple fix.

ok thankyou. Do you know if its the 1st or 2nd o2 ?

Also what brand should I buy for o2 sensors? Im on Rockauto , and the favorites are NTK, DENSO , but which one is better?

First off, stop changing sensors.

P0171 is a fuel trim lean code. Meaning the car is having to add more than 25% of the normally asked for fuel to reach proper O2 sensor switching. Normal cause of this is an air leak after the MAF, due to a vacuum hose rotted away, split open or something of that nature.

Check for any vacuum leaks, make sure all hoses are on where they should be and in good condition. On these cars, pay attention to the hoses around the bypass valve and solenoid, i've seen them breaking down after a couple years and they will create a small vacuum leak in the manifold that may not be very noticeable. If they looks suspect at all, change them out anyway.

An important piece of the diagnostic puzzle here is the actual fuel trim values. If the O2 reading is stuck way rich no matter what, it's possible you have a contaminated sensor or something similar. If the sensor itself fails, it will set circuit codes usually as well. If the car is trimming 30% on the fuel but then able to cycle properly, the sensor is fine but it's having to add too much fuel. Lean is either too much air or not enough fuel. Make sure you have fuel pressure where it should be, these cars have been known to have fuel pump failures and canister cracking issues which can result in lower than spec fuel pressures. Also change the fuel filter if it hasn't been done in the last 30K miles.

Last option, if this just started recently and you haven't had any other issues, is bad/poor quality fuel. If you get gas that isn't 100% gas, it has water mixed in it or what have you, then the car will have to add more fuel to reach Stoich returns from the O2. Once it goes back to getting proper fuel then this will correct itself. Just another option to consider.

Ok thanks. Ill be replacing the boost lines, and fuel filter, then go from there.

Ok, vac/boost lines and fuel filter did not fix anything and checked the air box , light came back on within 11 miles. Got the code checked at autozone. Search goes on.

Problem causes COULD be :

Maf - Replaced , and checked wiring.
Fuel pressure- Replaced fuel filter
Oxygen sensor - pending buy.
Ignition mis fire- WHAT DOES THIS MEAN, how could my ignition have a misfire, sparkplugs?
Fuel injector problem- I doubt that's it.

Misfire means the plugs maybe bad I would pull and check or replace if u have not done it in a while. I would go to the dealer for the o2 sensor these cars really like the oem o2 sensors had alot of problems with anything else

Also is this car been tuned or what. It could be a injector seal leaking not the injector itself

ok. Ill check the plugs, and most likely change them. Car has no tune.

Change your O2 and while your at it, check your connector/wiring as mentioned.

Pick up an aeroforce scan gauge and start logging your cars parameters.

Im guessing you guys mean the upstream o2 sensor (one on the header ) .

Yes.

ok thanks. o2 sensors are $96 bucks, so wouldn't want to buy the wrong one.

Yup, they can be pricey.

Make sure to purchase NTK (NGK) brand.

Ok, ordered a KTK from Rockauto with 2 day shipping for under 50 bucks ( ive had goodluck with rockauto ) , plus $50 bucks of saving sounds good to me. Local autostores said it would take 3-5 days for NTK, and they had a Bosch in stock but was still $71 + tax.

Will keep you updated. Thanks for the help.

Did changing just that O2 sensor fix your problem? Or the code pop back up again? I'm having same issue and thinking on just changing the upstream O2 sensor for being most common problem.

I haven't changed the sensor, weather has been horrible.. But I have noticed that when its warmer outside the check engine light comes off, and the car runs 10x better, when its colder outside, it runs like shit, and light comes back on.

I had this code awhile back, it turned out my catalytic converter was clogged.
Started off with CEL
then lack in power,
then car went into "limp mode" (display on message center was "engine pwr reduced")
and finally a few days later car sputtered out like it was out of gas then wouldn't start.

all this happened at around 75-80k miles

just some things to look out for not saying this is your issue just a heads up!

I had this code for while after I bought my car and couldn't figure it out, after searching for answers ppl kept saying get a tune. So I got a trifecta tune and it's been gone ever sense.