check engine

I replaced the exhaust manifold on my " Bullet " yesterday,. The original had a crack around #1. Replaced the front engine mount whilst the manifold was out of the way. Surfaced the collector tube, replaced the two gaskets, and buttoned everything up. Now the engine light comes on 3 seconds...

I need help and I am getting frustrated with my 2008 Honda Odyssey's check engine light that is now coming back up every few months. I have changed my Honda Odyssey spark plugs/coils at least 5 times within last 3 years and I think it might be time to take it in. I spent a lot of time trying...