Under Wisconsin law, a nonconformity is a condition or defect which (1) substantially impairs the use, value or safety of a motor vehicle and (2) is covered by an express warranty applicable to the vehicle or a component of the vehicle; nonconformity does not include a condition or defect which is the result of abuse, neglect or unauthorized modification or alteration by the consumer. 

A condition or defect that substantially impairs the use, value or safety of a vehicle must be more than a minor annoyance or inconvenience. However, the consumers vehicle need not have been undriveable for the nonconformity to substantially impair its use, value or safety. Also, the nonconformity may substantially impair use, value or safety even if the vehicle was able to provide simple transportation.

Wisconsin law requires a manufacturer or its authorized dealer to repair nonconformities. 

Duty to Replace or Refund (relief pursuant to sec. 218.0171(2)(b), Wis. Stats.)

Wisconsin law requires a manufacturer to provide the consumer with a comparable new motor vehicle or a refund if, within the term of the warranty or within one year after delivery, whichever is sooner, either:

The same nonconformity was made available for repair to the manufacturer or any of its authorized dealers at least four times and the nonconformity continued after the fourth time the vehicle was made available for repairs; or 
The vehicle was "out of service" for an aggregate of at least 30 calendar days because of any nonconformities ("out of service" is not limited to only those periods in which the vehicle is unavailable to the consumer; it includes those periods when the vehicle is not capable of rendering service as warranted due to a nonconformity, even though the vehicle may be in the possession of the consumer and may still be driven in spite of the nonconformity). 
The "same nonconformity" means the identical or substantially similar condition(s) or defect(s). A nonconformity is made "available for repairs" regardless of whether any repairs were actually attempted by the manufacturer or its authorized dealers.  Also a nonconformity is made available for repairs regardless of whether any nonconformity was verified at the time by the manufacturer or authorized dealer.

If repairs are not made and the consumer thereafter continued to give the manufacturer or its authorized dealers an opportunity to repair the nonconformity(ies), the 30-day clock starts running from the date of that initial failed repair opportunity. As long as there exists notice and opportunity to repair with respect to a nonconformity, the 30-day clock runs.

Duty to Repair (alternative relief pursuant to sec. 218.0171(2)(a), Wis. Stats.)

If a new vehicle does not conform to an applicable express warranty, and the consumer reports the nonconformity and makes the vehicle available for repair to the manufacturer or any of the manufacturers authorized dealers, before the expiration of the warranty or within one year after delivery - whichever is sooner, the nonconformity must be repaired. If the nonconformity is not repaired, the consumer is entitled to recover his or her pecuniary loss.

Enforcement (sec. 218.0171(7), Wis. Stats.)

If the manufacturer fails to replace or refund, or repair, as applicable, within a timely manner, the lemon law is violated and the consumer may file a lawsuit. A consumer who prevails is entitled to recover double damages, as well as attorneys fees and litigation costs