secondary air pump-check valuve

[c bausch]

Hey guy I did alot of searching on this one. I believe my air pump is bad ( jetsound on cold start ups) but I don'tthink get any codes. Yesterday I noticed when I got home from work as soon as I stopped and turned off the truck I heard a clapper shutting sound?? Im thinking its the check valve? I have been trying to search how to do a test on them both. I know im a little slowww...... but can someone please explain to me what I need to check first? Sorry for all the nonsense questions I have been asking

[Trail X]

I am admittedly not super familiar with this system, but I believe a jet sound on cold startup is a good thing.

The clapper shutting sound could be the throttle body closing.

Honestly, if your air pump is not throwing codes, don't worry about it. It's not causing any harm to your truck, it's only purpose is to heat up the CAT faster on cold startups as an emission reduction control.

[plaen]

I am admittedly not super familiar with this system, but I believe a jet sound on cold startup is a good thing.

Correct, as long as its only a few seconds I think 10 at the most.

I agree, no codes being thrown, I wouldn't worry about it.

[chevycrew]

My air injection is turned off in my tune, that may also be an option... (and rear O2 with a hollow cat)


(Edit: or at least I thought it was, but I may not even have it, now I need to go look....)

[c bausch]

But I didn't mention that first few seconds maybe 6 seconds I can see the exhaust almost sounds like its misfireing while the air system is doing its cycles then after that it runs fine, I guess my question is if my a.I.r system pump,valve is bad would it cause misfireing on first few seconds on start up?

[plaen]

But I didn't mention that first few seconds maybe 6 seconds I can see the exhaust almost sounds like its misfireing while the air system is doing its cycles then after that it runs fine, I guess my question is if my a.I.r system pump,valve is bad would it cause misfireing on first few seconds on start up?

My 07 sounds like that with the pump running, I would assume its from the extra air being pushed through the exhaust. After the pump spins down, it stops and the exhaust is normal sounding. If you don't have any lights I wouldn't worry about it.

My 02 doesn't have the air system, and sounds just like the 07 after the initial start up.

I don't know if the information made it to gmtnation or not, that may be a better resource for searching, although there is a lot of common members here.

[bdp1978]

Ive spent a lot of time dealing with the Air Pump issue. On a cold start the pump should run approximately 30 seconds and will sound just like if youve ever used an electric air pump to fill up an air bed---its essentially the same thing. It simply injects fresh air into the exhaust for emissions. The hoses will fill with condenstation and water in older trucks and should be disconnected and drained regularly. You can pull of the entire check valve and clean it, then using compressed air you can trigger it to open and close to see if its operating freely. The system is a total pain in the a$$ and I wish I could just eliminate it. There is also a grey relay right next to the pump that can go bad, but if youre hearing the noise youre pump is working.

As noted, if its not throwing codes then just leave it alone. Also to note is that if the truck is cold and you start driving before the air pump has finished its cycle it will cause the infamous "Lights Dimming" cycle while driving. Weird electrical glitch in these trucks.

[v7guy]

You've got pretty solid advice here.
The ECM knows if the check valve isn't working. If you hear a loud whine at startup it's the air pump. If you get a SES light you have a problem, otherwise don't worry.

I made an almost decent thread on gmtnation about it.

[fishsticks]

My air injection is turned off in my tune, that may also be an option... (and rear O2 with a hollow cat)


(Edit: or at least I thought it was, but I may not even have it, now I need to go look....)

We lucked out with 2002s. No MAF and no SAIS crap.