check engine light at startup.

[sweedrider]

When I first start my 95 f250 with 7.3l, the check engine light comes on and it idles low sounding like a duramax. After about 30 seconds or so the light goes out, it hiccups then sounds like a powerstroke as it should. My scanner won't read my trucks ECM for some reason. It has 250,000 miles on it. Please help.