dudes.. I'm driving the neon and the service engine light comes on. Unhook battery 5 min. goes out. I checked the milage and when I get to about 30 miles it comes back on. had mech. check all sensors and they are fine. I tried emission check before it got to 30 miles. Failed not ready.. it didn't have any check engine lights or sevice engine soon light. untill it drives 30 miles.

Any suggestions or idea's. Got stoped by the man last night cause my temp tag is expired. No ticket just warned get it fixed. need some help here.