: Secondary Air Injection System Fault ~FIX~

03-04-09, 09:55 AM
So I have been driving around with the check engine light on for a Secondary Air Injection System fault.


P0411 Secondary Air Injection System Incorrect Upstream Flow Detected

Turns out the check valve between the air pump valve and the tube that splits the air flow between the two exhaust manifolds was bad. I took it off and looked inside and found that it's not much different from a reed valve on a 2 stroke engine. Knowing that there are not to many stores that carry parts for our cars I decided that there had to be a better option then ordering it from the dealer for some outrageous amount of money. I went to my local auto parts store and asked for a air pump check valve for an 86 chevy S-10 ( a vehicle I knew had an air injection system). When he brought it out I thought I hit the jackpot. It was threaded the same and everything...best of all it was only $15 and I had it the same day. You do have to change out the spring clamp for a worm clam as the nipple is a tab bit smaller. I reset the code and it hasn't come back yet. Just thought I would share the info.

Here is the P/N for reference.

Gp-Sorensen / Air Pump Check Valve 779-2929

Motormite / Air Pump Check Valve 55050

03-04-09, 10:00 AM
I vote for a sticky, someone will find this usefull one day!

03-04-09, 02:22 PM
They are very similar.

Catera Check Valve

Chevrolet S-10 Check Valve

03-06-09, 07:09 PM
OK. I've had the same problem and I ignored it because it wasn't an issue. Where does it go or did I miss that?

03-09-09, 09:25 PM
Thanks for the info. I found it, replaced it and no more CEL.

03-13-09, 02:25 PM
Many, many thanks for this info Bubba1978. This code had been dogging me for over a year. I am going to this weekend to buy a check valve for a S-10 and be done with this silly code.

Thanks again,

04-08-09, 10:35 AM
Well, it's back. I'll have to fork out the $175 to Rock Auto. Hope you guys have better luck than I did!