1995 240sx se cel

[ka24ever]

This past Sunday I was driving up to a campground and my check engine light came on for the first time since owning it (~5000 miles). I pulled the codes yesterday with an OBD-II scanner and this is what I got:

1. P0400- EGR flow malfunction
2. P0420- catalyst efficiency below threshold (bank 1)

The car does have a hotshot header and a full HKS exhaust with no catalytic converter. Are the codes a direct result of this or is it an unrelated issue? If it is a separate problem, what is the proper course of action to fix it. I had read somewhere that the egr lines or the valve itself can get clogged and require cleaning, but that was specific to a maxima so I wasn't sure if the solution was the same. Also, could either of these be related to a faulty O2 sensor?

Thanks!

[s13sr20coupe]

searching really helps. Heres a place to get you started.

http://www.nissanforums.com/new-member-forum/27200-cel-code-p0400-egr-flow-malfunction.html

[chancelton]

Without a catalytic converter the p0420 will always be there
Does your header have a smaller pipe going back towards the engine? If not your egr code will always be there as well. If it does then there is likely a clogged pipe or port not allowing exhaust gas to flow properly. Or the valve/wiring to the valve is bad. Your next question is why did the light just turn on. Your computer likely just took a long time to set the monitors that keep an eye on those systems or you. There are multiple things that can keep a computer from setting monitors, such as coolant temperature and fuel levels.

[passergb]

There are multiple things that can keep a computer from setting monitors such as coolant temperature and fuel levels.http://goo.gl/eycghd