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Hey Guys and Gals!

My 2008 Cobalt LT (2.2 motor) has been throwing a check engine light regarding the secondary air system for about a month now, Multiple codes regarding it. Valve failed or seized causing water to get to the pump which too failed.

This week, i decided to fix it, i bought a new smog pump and a new check valve.
i swapped out both parts valve and pump.
Only code i get now is P0411.

when starting the car now the pump is active and i can hear it. i do not think i hear the valve opening or closing (i dont think its getting any power). the only code i am now getting is a P0411.(incorrect flow)

how can i test to see if the valve is working properly? what tests/checks can i perform regarding relays and fuses.

the smog pump fuse and relay are listed in the fuse box but i am unable to determine if the valve has its own fuse.

i am not getting the common sound of the valve opening and closing (tone change) with the air pump running and the system completing its cycle.

TLDR: how can i test the valve and its fuses; which fuses to check for the valve. how can i check the valve to ensure it is working with a 12volt power on its terminal.

has anyone encountered this before; P0411 code after a new valve and a smog pump?

i appreciate it thank you!
 

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forgot to mention car drives fine; no reduced power etc. only code is that P0411. i have been driving it to work and back without issues (60 miles).
 

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Dear Gopi: I am sorry to say that I do not have the answer. I do have a 2008 Chevy Cobalt LS with 2.2L Ecotec and also a P0411 Code (problem with Secondary Air System). Like you, I see absolutely no reduction in power, driveability, etc. , just the warning light on. Again, sorry not to help, but I would also like to know what to test and how. I have a 2005 Chevy Cobalt Repair Manual (PDF) which I can share with you and if the answer is buried in there, appreciate if you can let me know what you find out. The manual I have runs over 4,000 pages (Isn't that amazing?). I was going to research the Manual but haven't had time yet. Maybe we should both have a look. Or, if someone responds with the answer, that would be nice. Just out of curiosity, what were the other Codes you were throwing? I would hate to leave it until I get a failed pump and the damage escalates. I made the mistake on my old Toyota Sienna of letting problems go unfixed and it ended up killing the Van. Best, Reuben
 

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Dear Gopi: I spent a short while today trying to address my P0411 problem. First I started the Car and listened for the sound of the Air Pump but I am afraid I do not know what it sounds like and could not discern whether it is running or not. I don't know if I need to get under the car with a stethoscope, or reach it from the top, also with a stethoscope to hear if it running. I am thinking about that.

I started very late in the day (not too smart) and I did not have my headlight on, left it home, OOPS!). I started to unbolt the check valve assembly to see if I could spray it out with brake cleaner in case there was carbon buildup inside. Was not able to finish that up but did disconnect the rubber air hose while reconnecting the electric power. Went to the inside of Car and started up the engine and ran back to engine compartment and put my hand in front of the rubber hose to see if there was any air flow coming out. Could not feel any airflow which, if I am doing the right thing, seems to mean the Air Pump is NOT running.

Went to fuse box and the inside of the top cover is clearly marked with location of Air Pump fuse and what seems to be the Air Pump relay. I pulled out the fuse (in the dark) and looked at it with the headlights on. Looks intact to me. The next question is whether the relay (just in front of the fuse towards the front of the Car) is working. Haven't tested that yet. So, no resolution. Suppose I need to see if relay is working (assuming that is a relay I am looking at). And also need to figure out if the Air Pump is or is not running.

That is where I stand. Appreciate any comments from anyone on this matter. Thank you. Reuben
 

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Sorry. Started car this morning when it was good and cold after sitting overnight. Put my hand in front of disconnected hose going into check-valve assembly. Air flow was good and strong!! Nothing wrong with air pump apparently or associated fuse and relay. Took the check valve assembly off of mount (disconnected power) and sprayed out check valve with carb cleaner extremely thoroughly and remounted with all bolts, reconnected electric, etc. Cleared out P0411 diagnostic code from ECM. I will have to see if it comes back, can't tell you result. If the code returns, the problem is likely in the check valve assembly and very possibly the A.I.R. System Pressure Sensor within the assembly. Will see if code comes back. It could also be a problem with the wiring harness connecting to the check valve. That is all for now. Regards, Reuben
 

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Discussion Starter #6 (Edited)
Hey Reubenvabner,

Sorry about the late response! but my findings for just the P0411 only (after switching out the valve and pump) is that the passage way that leads to the exhaust is clogged. (an assumption at this point)

My reason to believe this is because if the Valve was defective (new or old one) it will have additional codes along with the P0411. and the same with the Secondary Air Pump.

The P0411 code is just stating that their is incorrect airflow; the other codes that come along with a bad valve or pump will also have a P0411 code along with other codes.

I checked to make sure my valve and pump are working using a LiveScan Tool. i saw both having activity; and opening for 20-40 seconds as it should.

When i did replace my pump; and disconnected the hose, Water (sewer like smell) it indicated that water was inside for a long time. (i have to admit my check engine light was on for about 4-5 months; didn't really matter because i was planning on replacing the car when registration time came)

I then had a buyer who wanted to buy my cobalt; i thought ill get it fixed for him so it will help someone else out; car ran perfectly no issues what so ever)

thats why i bought a new pump and valve etc to fix the car for the buyer.

TLDR: if you are only getting P0411 code (no other codes) chances are the passage for the airflow to reach the exhaust, once the valve are open is blocked.

also i do not know if the air direction sensor for the SAI system is in the valve or somewhere along the line.

I can hear the constriction of air flow when my pump is running; it does not sound proper, as it did when it worked. it does not sound free flow. - definitely sounds like compression taking place but no airflow for my car)

Sound might be a good indicator if your passage is blocked or not. (if you can hear the Tone of the SAI system change once its reaching its end cycle, then you most likely have free flowing air but the code is due to a faulty sensor (the one which determines the incorrect flow)
 

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also i do not know if the air direction sensor for the SAI system is in the valve or somewhere along the line.
 

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Just want to make final report on my Cobalt. Bought replacement check valve on Amazon. This was after checking that the air pump was running (on start up it blew a ton of air through the disconnected air hose going into the check valve. I had my hand in front of the disconnected hose and it blew plenty of air. Checked fused in fusebox but that fuse is for the air pump and since air pump is working did not expect to find it blown and it was not. There is a relay in there for the arir pump as well but did not test it - again, air pump is working.

Removed old check valve and installed new one. Did not tighten down the bolts to the exhaust manifold sufficiently and as a result had exhaust air escaping into the engine bay. Result was lots of exhaust noise and reduction in engine power and performance as you have exhaust going backwards through a small constrained opening resulting in tons of back pressure, etc. At least that is my diagnosis.

Got home, took the check valve off again and reinstalled making sure the bolts into the exhaust manifold went in properly and tightened them down fully. Took a while to find the bolt holes and thread them correctly as you cannot exactly see what you are doing, it is all by feel. Seemed they were tightened up good. Sprayed out the electrical connector and reattached it. Back flow of exhaust gone and P0411 code has not come back after driving 400-500 miles.

As an unskilled DIYer, kind of proud I solved one problem on my own. Check valve cost like $130 on Amazon. Think it was AC Delco. I imagine it would have been a lot more bucks at a garage. It occurred to me that the check valve must close off the opening to the exhaust manifold when the air pump finishes its 30-35 second run at start-up. Otherwise, you would have that backflow that I mentioned and, I guess obviously, the purpose of the check valve is to shut down the opening. I guess it was stuck in closed position in order to generate the P0411 code before fixing. If it was stuck open, would have been a lot of exhaust noise, reduction in power, etc. as I experienced when I did a bad installation.

Any thoughts, let me know. Issue closed for me. P0411 gone. On to next Cobalt problems: mystery slow oil leak, a bit of leaking transmission fluid from the hose running to the radiator. Leaks are so f'ing annoying. Transmission fluid leak should be fixable with a tight clamp on the hose where it meets the metal end of the hose. Oil leak I have been struggling to find for a long time. Believe it is the oil pressure sensor at this point.

Best, Reuben
 

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also i do not know if the air direction sensor for the SAI system is in the valve or somewhere along the line.
Gopi. Thank you. I had already written about the end of my P0411 adventure before noticing that you had replied. Thank you for replying. I believe that sensor is in the check valve assembly and probably was the part that went bad and kept the check valve closed thus blocking off the air flow coming from the secondary air pump. I did notice some carbon buildup in the opening leading into the check valve but not enough to entirely close it off. I conclude that the sensor (already said this) was bad and the check valve was locked in the closed position thus letting no air flow into the exhaust stream and the P0411 was the error from the ECM detecting that there was no air flow going to the exhaust stream on start up. So I am already now (see my previous posting two minutes ago. Thank you for interacting with me and sharing experiences. That is how we both learn. You know a good amount as in knowing to listen for the sound of the air pump kicking in. I tried to do the same thing while my wife started the car but I could not clearly pick up a distinct whine. Disconnecting the hose going into the check valve and putting my hand in front of the hose as my wife again started the car up (on a different day) told me clearly that the air pump was fine and the problem was either the check valve or electrical. Thank you and best wishes, Reuben

Now if you could tell me how to get the oil pressure sensor out and replace it, I would be forever indebted. I can see where the electrical runs to the oil pressure sensor but really can not see all the way to the sensor and am wondering how I get a socket wrench on it. Also lots of electric harnesses and some hoses running in front so wondering if I can find the oil pressure gage with my socket wrench, turn the wrench (I think I am spelling wrench incorrectly ??), get the old sensor out and feel with my hand as to opening to start to screw in the new sensor by hand and then socket wrench it in. Again, I am not an extremely skilled DIYer and when I don't have a straight line of vision to a problem area, I wonder if I can do it purely by feel without vision.

By the way, trying to do something else the other day, I dropped an 18mm (1/2 inch socket end) socket into the spot I was working on and it disappeared, rolled someplace. I spent on-half hour trying to find where it rolled to (it was NOT on the ground under the Car), so there went my 18mm socket, disappeared somewhere in the engine bay. Maybe if I lift out the engine, I will find it (no. will not do that).

Signing off, Reuben
 
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