(Reuters) - Some 2.1 million vehicles produced by Toyota Motor Corp, Fiat Chrysler Automobiles NV and Honda Motor Co are being recalled to fix a potentially defective chip that could cause air bags to deploy inadvertently, U.S. federal vehicle safety regulators said Saturday.

The vehicles were subject to three earlier recalls, but the National Highway Traffic Safety Administration said in a statement that "a small number of vehicles" fixed under those earlier actions had experienced inadvertent air bag deployments.

The recalls were not related to a wider issue involving millions of vehicles recalled over Takata Corp (7312.T) air bags. Takata, a Japanese air bag maker, has been involved in massive recalls worldwide.

NHTSA blamed the problems it reported on Saturday on "electrical noise" in the air bag system. The agency said a fully effective solution to the problem might not be available until late this year.

The NHTSA said the models affected were: 2002-2003 Jeep Liberty and 2002-2004 Jeep Grand Cherokees (about 750,000 vehicles); 2003-2004 Honda Odyssey; and 2003 Acura MDX (about 370,000 vehicles) and 2003-2004 Pontiac Vibe; Dodge Viper; and Toyota Corolla, Toyota Matrix, and Toyota Avalon (about 1 million vehicles, not all of which were sold in the United States.)

Although the recalls announced by the agency are not related to the Takata cases, the NHTSA said there was an overlap, in that about 1 million of the vehicles affected were also covered in separate recalls of Takata air bag inflator systems.

The latest recall highlights the difficulty automakers and regulators have with increasingly complex electronic systems. The agency said in a statement it could take several months for the companies to get enough parts to fix all the vehicles involved.

(Reporting by Joe White; Editing by Frances Kerry)