G.M. Scales Down Nikola Deal

General Motors and Nikola, a high-profile start-up aiming to produce electric trucks, said on Monday that they had reached an agreement to work together only on hydrogen fuel cells, replacing a broader alliance they originally outlined in September.

The new agreement calls for G.M. to sell fuel-cell technology to Nikola. Gone are provisions for G.M. to take a $2 billion stake in Nikola, and for G.M. to produce an electric pickup truck for the Phoenix-based company. Nikola said it no longer planned to produce that pickup, the Badger.

September’s announcement had lifted Nikola’s stock and investor confidence in the start-up’s ambitious plans to develop heavy trucks powered by hydrogen fuel cells and a national network of fueling stations.

But just days after the Sept. 8 partnership announcement, a small investment firm put out a report asserting that Nikola and its executive chairman, Trevor Milton, had greatly overstated how much technology the company had developed. Later that month, Mr. Milton resigned.

Nikola’s stock was down about 20 percent in morning trading.

This is a developing story. Check back for updates.