Thomas Siavash, 59, of Fargo, was issued a summons for reckless driving and driving under suspension, authorities say.
WDAY says Siavash's license was suspended for DUI in February and he was coming to the jail for his twice-daily breathalyzer, which is part of a 24/7 program.
Fargo police said it didn't appear that alcohol was a factor, nor do they think the act was intentional.
Even though authorities said Siavash didn't say anything to indicate a threat, Cass County officials called in a bomb squad for extra precautions.
A search of the car by bomb squad robots turned up no explosives.
Sheriff Paul Laney told WDAY that he took precautions because the incident appeared suspicious.
"After what happened in Boston and what happens around the world, when a car goes that perfectly through our doors, we have to think 'car bomb'," Laney said.
The Cass County Jail houses 205 inmates and has 30 staff members.
The jail doors were replaced later in the day.