The state of Maine requires all motor vehicles to undergo a safety inspection once a year. Vehicles registered in Cumberland County are also required to undergo an emissions test. We contacted the Maine State Police regarding your question and they informed us that there is no grace period with inspections.
The inspection sticker is valid until its normal date of expiration even if the vehicle fails inspection; however it is a violation of Maine law to operate a defective vehicle even if the inspection sticker has not expired.
You cannot though drive during the time that your car is listed as failing its inspection or being non-compliant. Furthermore if you fail to make the repairs and have the vehicle re-inspected you face registration suspension and a citation for a defective motor vehicle.
So if your car does not pass inspection in Maine you will need to get the issues fixed and get the car re-inspected, so that it passes inspection this time, before the inspection sticker on it expires.
Being caught driving without an inspection sticker is a traffic infraction. Unless otherwise specified by the jurisdiction you are in, this is a Class E crime, which is punishable by a fine of not less than $25 nor more than $500 or by imprisonment for not more than 30 days or both.
For more information about motor vehicle inspections the Maine State Police said to call 207-624-8941.