Like 71GTX471 said, not sure how it is state by state, but here in WI you are allowed some unset readiness indicators based on year. I think WI is identical to what he said or close - I just had to nurse my dad's 99 Buick through with 2 I could not get to set. Some of the older cars it is a real bear to get them to set, and I believe emissions people have realized that hence the rule.