Hey guys, long time lurker, first time poster. I've had my 2006 2.4L HHR LT for around six months now. I recently got around to installing some modifications and decided to install a cheap eBay intake - as I have had good luck with them on other vehicles. The particular intake I purchased was technically for a 2.4L Cobalt, but it fit in the HHR just fine. The MAF sensor fit perfectly as did the PCV line. However, I am now getting a P0171 code. I have reset the code several times but it returns within a few miles each time. The issue that I am having is that I am unsure what is causing this code.

Just before installing the intake, I filled up with gas from a station I had never visited before. I immediately noticed that the gas caused a bit of a fowl odor coming from the exhaust. Nothing unbearable, but the exhaust definitely smells a little off. I know that "bad" gas can cause a P0171 code. I was unaware, however, that these cars require 91 octane fuel. I should also note that I had a pending CEL code in the days leading up installing the filter, but I wasn't able to get home and scan it before it cleared itself. This leads me to believe that poor quality gasoline could be the culprit here, but I can't confirm that the code was a P0171. It could have merely been a coincidence.

Next is that, while installing the new intake, the MAF sensor slipped out of my hand and onto the carpeting in the back of the car. I only fell about 3 inches, so it seems unlikely that this damaged anything. I immediately cleaned it using MAF cleaner, but that also makes me wonder if this could be causing the code.

So, my question is: what do you guys think is causing this? The new filter setup, the potentially "bad" gasoline, or a faulty MAF sensor? I hate to return the filter setup, because the performance boost is very noticeable and I'm hoping to get better mileage with it. I especially hate to re-install the factory air box and have the issue persist.

 

https://www.obd-codes.com/p0171

Welcome to the site, check this causes and solutions. Is the CAI an oil filter or dry filter?
Any possibly the intake manifold has a crack or gasket problem.
is the MAF connector tight , no loose pins?

 

Probably the "cold" air setup. (They are usually the opposite of their name, sucking in hot, underhood air) Lots of folks have experienced CEL's from installing those so called Cold Air setups. The Ecotec engines are pretty finicky when you start messing with the preset air flow parameters. In other words, the computer sees different air flow as something wrong.
Plus. There really isn't any gain from those CAI systems unless you tune for it.

Best way to tell. Put the original filter setup back on, clear the codes and go drive it and see if the code comes back. My guess is it won't.

 

I'm gonna say it's that intake as well...

Also on the fuel... The 2.4L is high octane Recommended. Not high octane Required. There is a difference... That being said I've had mine tuned for 93 octane and that's all I use. They didn't come from the factory this way though.

 

Take it off and put the stock back on, reset the code. If it doesn't come back you have your answer.

 

I take strong issue with the obd2 codes website on this one. GM describes the P0171 code as "FUEL TRIM System Lean" not bank 1 too lean; these are opposite each other.

 

The MAF sensor drop could have damaged it, they are fragile sensors.

About the fuel:
Since the car is now detecting a lean fuel mixture it compensates by making the car run rich. So even though you are getting a code for running lean, you are smelling the gas by the exhaust because the car is running rich.

Fix it quick, so you don’t damage the catalytic converter.

 

Fuel trims are complicated.

The O2 sensor sends a signal to the ECM saying that there is a lot of oxygen getting to it, The computer thinks "that must mean that there is too much fuel in the A/F causing an incomplete combustion" so it Trims LEAN. The O2 sensor senses O2 not exhaust gas because it can't control the amount of air only the amount of fuel.

So, in actual "real world" P0171 means there is a air leak causing the sensor to send the correct signal but the ECM mis interprets it. "Why would you bother me with a condition I have no control over? I will do what I can to force the O2 sensor to send me the right data".

It means the TRIM is lean, not the mixture. There is unmetered air getting into the system between the MAF and the O2 sensor, or a sensor is malfunctioning.
I hope that makes some sense.

 

As pointed out in the link I posted, an air leak in the intake manifold side , gasket, broken brake booster hose bib, loose hose to the throttle body, loose throttle body

 

Just wanted to update everyone about how I fixed the issue. I woke up this morning and noticed that I had 2 lean codes, a MAF sensor code and an O2 sensor code - all of which came about after installing the aftermarket intake. I ended up having to put the original air box back on, but I made somewhat of a hybrid setup between it and the aftermarket intake.

I removed the standard air filter from the air box and I removed the hosing that sucks in fresh air from the fender. I then installed the aftermarket cone filter where the fresh air hose used to be, buttoned it all back together and all of the lights went away and have not returned. The car doesn't run quite as well as it did with the aftermarket setup, but it certainly runs better than stock. It's much smoother and quieter, but I haven't confirmed if the gas mileage has improved yet - and that was the entire purpose of this project. The strange thing is that, you would think the aftermarket intake would have allowed *more* air to flow into the engine, right? Well, according to my scan tool, the aftermarket filter was pulling in about 2.3 grams of air. This is almost perfect for a 2.4L engine. However, the factory air box was pulling in a consistent 2.6 grams of air - *more* than the aftermarket. This makes no sense to me, but I am satisfied with the end product. I just wanted the car to run smoother and get a tiny bit better gas mileage.

My idea behind removing the fresh air hose and installing the cone filter is so that the intake will be sucking in warm engine air, rather than cold outside air. In theory, this should bump gas mileage up a tiny bit. I ended up getting a refund for the aftermarket kit, but was allowed to keep it. So my total investment in this setup is $3.99 for a new PCV hose. Hopefully the gas mileage will increase enough for me to recoup my $3.99. ha.