Check engine code 400 EGR valve

[Zoltan11]

Looking for some tips on checking changing or cleaning my egr valve and hoses.
I have a 2000 I30 with 130k

[loystock]

Welcome to NICO.

That fault code is not showing for the 2000/2001 I30. Very strange.

The link below will give you an idea about EGR and related components cleaning. It 's for a 98 I30 but I believe your car's engine is similar.

valve-cover-gasket-job-on-i30-very-thor ... 90767.html

[Zoltan11]

Had my code read and 400 came up again. You seem to be correct about that code not applying to the 2000 i30. My car was actually manufactured in oct 99 so I wonder if that codes for the 99 I30 are the same. I'm thinking about checking the egr stepper motor to see if the valve is working. Anybody done that before?
Thanks

[loystock]

The P0400 is a valid trouble code. Most likely the problem is due to clogged EGR tube (carbon build up).

[Zoltan11]

Ses light back on after several thousand miles of being off during the cold months here in Colorado. I started this topic several months back when it was still quite warm. (above 45 F. ) My SES light turned itself off once it got below 40 consistently. It remaind off as long as it stayed cold. It turned itself on again when there was an unusually warm week. Then it turned itself off again once it got cold again. It's been above 45 regularly for the past week and now the light is back on. I should mention that I drive 500 miles a week for work. Part city part highway. The code seems to be triggered when coasting down to lower speeds from highway speed when it's been warm for at least a few days. Since temp seems to be a big factor should I be looking into the temp sensor instead of the common carbon build up in the egr tubes? I have read a number of other posts saying they replaced and or cleaned a lot of the egr system components only to have the same code pop up again. I even read that one guy did everything only to find out the problem was only a leak or something in the air box. Anyone got any thoughts?
Thanks