P0174 and P0171 Code Help

[piperbrannin]

Hello, I drive a 2010 Camaro 2ss with the automatic L99 engine. My car is clean title, 55k miles, and extremely well maintained. Within the last couple months my car started throwing a check engine light and codes for P0174 & P0171. It began with throwing these once every few weeks, but it has started throwing the codes more recently (every couple days to a week) which is strange since I haven’t changed anything before the codes switched.

I can’t seem to find much info on how to diagnose this issue. I am not very mechanically inclined and would love some help. The car seems to bog more than it used to and I’ve noticed some exhaust “drone”(almost sounds like an exhaust leak) when I’m not on the gas much, but goes away as soon as I give it some gas. The exhaust is a Borla Catback ATAK exhaust and has never made this noise until after the engine lights started appearing. The car has a fully enclosed CAI with no tune and no other mods done to it.

I have changed all spark plugs and connectors(OEM), replaced PCV hose(OEM), cleaned the throttle body, cleaned the MAF sensor, checked all connections via carb cleaner to check for changes in idle, checked CAI connections and filters. It still is throwing the code but has recently changed to only bank 2 P0174. I’ve heard it could have something to do with the o2 sensors and have read you can switch the sensors around to see if the code will jump to the other bank, but I have not tried as I figured if those were the culprit both would be faulty as it used to throw both bank 1&2 codes.


Please let me know if you have any ideas or possible causes for this, thank you!

[bottletalk]

if ur hearing an exhaust leak get under the car and find it, if there's a leak it can give u a lean code.

[bottletalk]

without live data it's a guessing game.
if u have an android phone get yourself a bluetooth obd2 wireless connector, download "torque"(the full paid version) and go online and check ur o2's and fuel trims. makes finding problems ez, it'll be the best $40 u ever spent!

[piperbrannin]

Originally Posted by bottletalk

without live data it's a guessing game.
if u have an android phone get yourself a bluetooth obd2 wireless connector, download "torque"(the full paid version) and go online and check ur o2's and fuel trims. makes finding problems ez, it'll be the best $40 u ever spent!

I actually have a scanner tool that shows live data for all my sensors/fuel trims. What should my short and long term trims be at? I’ll plug it in tomorrow and keep a log of the numbers throughout my drive.

[piperbrannin]

Originally Posted by bottletalk

if ur hearing an exhaust leak get under the car and find it, if there's a leak it can give u a lean code.

I’ve looked underneath the car and at the exhaust and can’t find any noticeable leaks or bad fitment. It is a catback exhaust, would this affect anything as the debris are all before the aftermarket exhaust? Cats are still on

[Nate2SS]

Originally Posted by piperbrannin

I’ve looked underneath the car and at the exhaust and can’t find any noticeable leaks or bad fitment. It is a catback exhaust, would this affect anything as the debris are all before the aftermarket exhaust? Cats are still on

You could have leaks anywhere that aren't visible to just looking. You can smoke-test the exhaust to see if it leaks anywhere. The LTFT gives you the best idea of how it's running. They should be as close to 0 as possible. It's the oscillation of lean and rich so you will never have a perfect 0. It should never range past +/- 10% on any car. Some people are more stingy and require a tuned car to run within 5%. I have no idea what a stock car range could be, but if it's enough to throw a lean code, I imagine it's past 10%.

[bottletalk]

i think %25 triggers the lean alarm.

first: u said that u hear a possible exhaust leak, follow the sound and locate it, u might have a slightly plugged cat and the back pressure is forcing itself out....
second: go through all the live data and see if anything is odd: do the numbers that u see on bank 1 compare to bank 2? o2's passenger vs o2's driver side(can't remember if 1+2 is on the same side or if it's 1+3)? then set up some trends and monitor ur o2's, fuel trims and exhaust /cat temps..,ur temps are the important part cuz a heater on the o2 sensor could be toast(fused) and it'll tell u if your cats r good...assuming all ur other data is fine.
right now I'm guessing a bad o2 sensor, bad cat or exh leak.

[morepowerjoe]

I just wonder if o2's being that old would start to degrade in it's reading abilities? I know I've heard to change them at 80-100k miles but never on how long they actually last.

[acutron42]

Originally Posted by piperbrannin

I actually have a scanner tool that shows live data for all my sensors/fuel trims. What should my short and long term trims be at? I’ll plug it in tomorrow and keep a log of the numbers throughout my drive.

Check your fuel pressure for about 60 psi & your maf sensor for about 1800 hz as long as you have the capability.

[Mouse330]

Hook up your scanner and watch live data of the LTFT's Your probably gonna see them around +25. Disconnect the MAF and retest, Your should see the STFT go negative to try to bring the LTFT back down, Also check the air intake tube for splits/cracks, I'm pretty sure it needs a MAF sensor.

[piperbrannin]

Here’s a little update on the issue:

Replaced MAF and actually sealed it into the fitting at a shop(thought it may be the leak but wasn’t)
Checked the fittings/clamps on my CAI
Cleaned/checked throttle body and MAP
Smoke tested the entire engine(no leaks found)
RPM needle bounces at idle(heard this may be common due to the aggressive stock cam on the Camaros)


It’s going back into the shop a third time this upcoming week, but I think it may be a fuel injector/fuel system issue as we couldn’t find any vacuum leaks and all sensors seem to be doing their job and can’t find anything wrong with them.


Only throws the codes at idle, never when being driven. Typically right after starting or 10 seconds after starting.

Thank you for your help, the shop has seen it twice now and it’s still throwing codes:
P0171 and P0171

[Rock-It Man]

I know I know; this is so redundant, but please, get a new battery before swapping out more expensive parts. So many built in test systems go batty due to voltage drops.