02 Frontier 2.4XE P0400(but gone in winter)

2002 Frontier 2.4 XE king cab 2 wd in northern Minnesota. Check engine light (code P0400) is on 10 months out of the year. When January comes around and temps are 15 degrees or colder its off until weather gets into the 20's and warmer-then light on again. I found the 4 ports in the manifold plugged and cleaned them but didnt help. The truck runs fine, has 125,000 miles.
Thanks David