O2 Bank 1 replaced

P0402 is for EGR flow, nothing to do with O2 sensors or that CAT. This is why you can't trust parts store-script-reading-employees. Get your own scan tool and carefully research things first. Have you done anything to address the orginal EGR issue? or maybe you misstyped and ment to say P0420? that would make some sense of the story.

 

Yep, I'm pretty much done with the parts store. Going to order a scan tool myself. After reading your reply about the
EGR I did some research and seems I fall into alot of the symptoms a faulty EGR creates. Thanks again for advice.

 

The components to start with on that EGR code are the vsv and the modulator and the hoses that connect to them, little vacuum hoses that you want to make sure aren't plugged up with carbon and crap.

 

Where are you buying these Denso sensors? There is a huge market for fake denso parts out there. Id only buy an O2 sensor from Napa or the dealer. If you buy online, theres a good chance its fake.

 

I bought the sensors from OReilly. I think I have narrowed down the problem. A friend of a friend changed the cat for me. I don't drive the truck very often but I did notice a difference in the sound of the exhaust but didn't think much about it. It was louder than it was before changing the cat, almost like it was bypassing the muffler to some extent. I crawled under the truck and noticed the connection between the cat and muffler was not sealed tight, look as though the flanges didn't bolt up tight. After more looking I noticed the guy who installed it had cut the flange from the old cat and welded to the new one and didn't get it completely square so when the flange meets the other flange at a slight angle they can't seal up tight. Searching into this I came across a trouble shoot that said I could get an error for the second sensor due to exhaust leak, which is what I think is going on. Lesson learned. Will have a real exhaust shop fix. Thanks all who helped or lent advice.

 

So Rock Auto isn't trustworthy ?

 

They should be. I'd be surprised if any of their suppliers (or themselves) would ship counterfeits. Rock Auto is probably a safe bet