How long did Detroit auto makers shut down during WWII?

I imagine they converted to war manufacturing, but when did the auto companies stop making commercial vehicles during World War II? And for how long?

every industry that wasn’t making essential goods went into war production either in the same industry or what ever that factory could produce.

Ford continued to make a few 1941 models into 1942. They produced no civilian cars through the war, and restarted with a 1946 model, which was virtually identical to the 1941-2.

Well,except for Dusenberg - which was seized by the Federal Government due to the Dusenberg brothers being German nationals.
Of couse, the Federal Government locked up everything nice and tight, so the Dusenbergs could resume production after the war.
Yes, and the Toothy Fairy, and Santa are humping at this very instant!
That factory was picked clean, and the Dusenberg never returned.

The Duesenberg brother were born in Germany, but emigrated to the US at the ages of 5 and 8 years old. They founded their motor company in 1913, but it struggled financially and in 1926 they sold it to Auburn Automobile (founded and owned by the American-born E.L. Cord). Thereafter they were employees of the corporation, not owners.

Thus, by the time the US entered the war, Duesenberg was a wholly US-owned business. Or would have been, had it not in fact ceased production in 1937, when Auburn Automobile itself collapsed. It was the Depression that did for Duesenberg, not the war or wartime expropriation.