Complex sentence: Production of the Combo C ended in late 2011 in time for the December 2011 launch of the Combo D, which is based on the Fiat Doblò.
Split into simpler sentences: Production of the Combo C ended in late 2011, when a new Combo based on the Fiat Doblò was launched. The third generation has been manufactured from December 2011, and is based on the Fiat Doblò.