08 p0411
 

Hello
I have a 2008 trailblazer and a light came on a few days ago. The code reads P0411, secondary air injection system, incorrect flow. Do I need to replace the secondary air injection check valve? Will it hurt anything driving it like this? Is there a workaround? Thanks.

V6 4WD auto

I had this problem on my 05 TB.

The check valve may be opening only part way, it may be stuck open or closed or the pump might not be working properly.

The secondary air injection system is designed to add filtered air into the exhaust manifold to help complete combustion of products in the exhaust gases and minimize pollutants. An air line comes from near the air filter and leads through the pump and then to the check valve.

During normal operation the system runs when the engine is started cold. As soon as the exhaust gas temp rises the pump turns off. The check valve opens when the pump is running and closes when the pump stops.

If the check valve sticks open after the pump stops running, hot exhaust will enter the line from the pump. The moisture in the exhaust will condense in the air line and collect at the lowest point, which in my vehicle is at the pump. The water will damage the pump. This will happen quickly if the vehicle is stored in below freezing temps.

Check the check valve for proper operation. Also check the pump. In my case the check valve must have been stuck open for a long time because there was plenty of water in the line and the pump had completely failed. I had purchased the vehicle used and was unaware of the problem until a few days after purchase.

I ended up replacing both the pump and valve. Fortunately the party who sold me the vehicle helped with the purchase of parts. I installed the new parts myself. They are fairly easy to replace.

It's been 10 months and no light has come on again. I recently checked the line by the pump and found it dry.

Has anyone had this repaired at a dealer? If so, what did it cost?

The costs will depend on what needs replacement. In 2010 I replaced the check valve and the pump.

The check valve was a GM product and cost about $125.
The pump was a little more expensive and I purchased it from a discount auto supply business but the part did have a GM part number. I think I paid about $150 for the pump.

Since I replaced the parts myself I have no idea about the labor cost. Total time at a dealer should be less that 2 hours labor.