Code P0404

Ok I have a '98 Astro 4.3l 2wd. Its throwing code P0404(SES light) which is EGR range perf. It only seems to throw it if its really cold out like -10f or more. Its happened about 3 times now first 2 times it erased itself overnight so I didnt worry about it to much. Just gave her a tune up plugs, wires, cap, rotor since it was due. Now it threw the code again and hasnt cleared itself in 2 days. So is my egr shot or is there anything else that could be causeing it to throw the code? Just trying to minimize my exposure to frostbite diagnoseing the issue so any ideas appreciated.
edit: Its seems to run fine if the SES light is on or off, no missing or anything to the effect.