DETROIT (AP) — Hyundai is recalling 173,000 Sonata midsize cars in the U.S. because the power steering can fail, making them harder to steer and increasing the risk of a crash.

The recall covers Sonatas from the 2011 model year when the car was Hyundai's top-selling U.S. vehicle.

The company says in government documents that the computer circuit board in the power steering control unit can become damaged. If that happens, the cars would still have manual steering, but it would take more effort to turn the cars and could cause a wreck.

Hyundai says it's not aware of any crashes or injuries from the problem. The company started investigating the problem in March of 2015 after getting warranty claims. Investigators found the circuit boards could fail over time when exposed to the environment.

The recalled cars were built from Dec. 11, 2009 to Oct. 31, 2010. Cars built after that had an improved protective coating over the circuit board.

If the control unit fails, drivers would see a warning light on the dashboard.

Hyundai will notify owners and dealers will replace the control unit at no cost to owners starting May 30.