When General Motors and Toyota established a 50-50 manufacturing venture in Fremont, California, back in 1984, they agreed to run things the Toyota way. Workers would operate in small, close-knit teams, parts deliveries would be timed to the minute, and every worker would have the power to stop the production line when something went wrong.

GM has now reached for the stop button, saying it will sell or wind down its interest in the operation as part of its court-supervised restructuring. Toyota must now decide whether to run the whole Fremont plant itself, find a new partner or shut it down, jettisoning 5,500 workers and manufacturing capacity of a quarter of a million vehicles a year.