70camaro

This happened on my '97 GMC 5.7L, but I'm sure the info is good for lots of other applications.
If your SES or CES light came on and you pull a P1406 code from your PCM, try this before you pay a shop to fix it:
Remove your EGR valve and soak it in about an inch of good carbon cleaner. Dont submerge the whole thing, just the bottom part where the valve seats. Leave it overnight and clean it really good the next day with a pick and a brush. (a small screwdriver and an old toothbrush work just fine.)
Push open the valve and carfully clean any carbon built up around the valve and seat. The valve should move freely and NOT stick in the closed position. When the valve is dry, reinstall it and clear the codes.
It worked for me, and could save you a trip to the shop. Good Luck!