U.S. safety regulators opened two separate safety investigations into Chrysler Group LLC's 200 sedan due to complaints of engine stalling and Ford Motor Co's Explorer SUV for steering problems.

Both vehicles are for the model year 2011. The two probes potentially affect more than 170,000 vehicles.

The National Highway Traffic Safety Administration said in a posting on its website that it received 15 complaints about 2011 Chrysler 200 equipped 3.6-liter engines. The vehicles stalled without warning when the driver was decelerating at low speeds, such as braking for a stop light, according to the complaints.

NHTSA's department of defect investigations also received 15 complaints about Ford Explorer vehicles equipped with electric power assisted steering. In those incidents, drivers reported a loss of power steering and the need to apply more effort to steer the SUV.