Can't figure out the cause of my P0411 code

[awwende]

Had the code on for a while now, I originally had another code saying the secondary air injection valve stuck on bank one, so I replaced the check valve and the check engine light turned off for a while.

A few weeks later the light came back on, this time it was the P0411 saying there's a problem with the air flow. Tested the air pump and found that to be faulty, also found the fuse was blown so I replaced that as well. After clearing the code, it came back on later that day with the same code. I double checked the check valve and saw the solenoid was measuring about 15 ohms, and I checked the solenoid valve fuse, and that's ok.

One of the symptoms my engine is having is during the test I believe it increase the fuel mix to run rich, and then the ECU reads the O2 sensor to make sure the O2 value goes up when the pump kicks on, but what I'm seeing is even though I can hear the pump running, my engine starts to stall, most of the time it recovers and the RPMs jump up to about 2k, then return back down to about 800-900. Other times it completely stalls and I have to restart the car.

Does anyone know what the problem could be?

 

[onedoughboy]

Your exhaust manifold gasket could be bad or leaking.

Do you live in a state where there is emission testing? I live in Michigan, we don't have the testing, but I have some experience with the California emission vehicles. I have noticed a pattern of cracked heads. While there is no difference in the head, the exhaust manifold is different, and the air pump blows cool air thru it into the head. Doesn't sound like a good idea to me, but it helps fewer parts per million come out the tail pipe. The problem is the heads are cracking by the manifold. My solution in Michigan, replace the head, and manifold(/w fed emission), then reflash the pcm as federal emission. This does away with the air pump, check valve and other problems. I know someone is gonna jump down my throat and say it's illegal to mess with the emissions, but honestly if you live in a state that doesn't test for it, what's the problem. If you live in a test state, its a different story. The price of a new air pump, the check valve, and the plastic plumping tubes on these vehicles can easily reach about 600 - 800 in just parts.

---------- Post added at 10:40 PM ---------- Previous post was at 10:00 PM ----------

On a different note, your stalling might not have anything to do with your code. You might want to check for a vacuum leak around the intake manifold, clean your mass air flow sensor and electric throttle unit, check for cracked intake, or lose intake plumbing, and the little hose from the valve cover to breather, they are starting to dry rot and crack. Try snugging down the bolts on the intake and electric throttle. Any vacuum leak after the mass air flow can cause or contribute to a stall.

 

[YelloEye]

Remember not to move the butterfly inside the throttle body by hand, you'll mess up its calibration and it'll be a great paperweight.

You can clean around it by turning the car on without starting it and pushing the gas pedal to the floor and holding it.

 

[onedoughboy]

You can recalibrate the butterfly with a good scan tool. But honestly, I've never done it, or had to do it. And I always move it with my finger, though I probably don't do it with the key on. I have changed quite a few of them as well. They tend to get hit in every front end accident. Have to open them up and look to see if plastic pieces from a smashed air breather are floating around inside the intake. It's a good unit, I've never had a problem with one, with the exception of it being smashed or broken wire, broken connector. My very first cobalt I fixed, back in 2007, was sold to my sister, she has almost 180k on it now. The throttle opening was bent and I straightened it with a muffler spreader to make the open round again. Back then they were very expensive, now I have a bunch on a shelf collecting dust.

 

[YelloEye]

I've never seen an off the shelf scan tool that can recalibrate the throttle body. I imagine a Tech2 can do it but nobody wants to drop $1k+ for the thing.

In my limited experience, anytime you push the blade by hand you end up idling high. That might correct itself IDK.

 

[onedoughboy]

I was thinking of my old Snap On Solus. Cheap china Tech2 will do it to. Either can be found pretty reasonable today. Maybe even an OTC Genesis.

 

[awwende]

After a little bit to let my frustrations simmer, I went back to check over everything. Turns out one of the two pipes on the air pump wasn't connected all the way. This was a result of big hands, tiny space to connect the pipes and terrible/cheap snap connectors on the pipe. Once I refitted the pipe, the error code went away.