Unable to reach an agreement by the strike deadline of midnight last night, members of Unifor Local 88 have hit the picket lines at Cami Automotive in Ingersoll.
The union and General Motors spent the afternoon and evening at the bargaining table but could not hammer out a deal.
There is no word on when negotiations will resume.
Unifor Local 88 President Dan Borthwick is asking members of Local 88 to go to their website to check on picket duties.
Cami manufactures the Chevrolet Equinox crossover but recently lost production of the GMC Terrain and about 600 jobs to Mexico.
There are 3,000 workers at the Oxford county plant.