TORRANCE, Calif. -

Now the oldest versions of the Toyota Prius are being recalled.

Toyota Motor Sales USA announced Tuesday it will conduct a voluntary safety recall involving approximately 52,000 Prius vehicles sold in the U.S. from the 2001 through 2003 model years. The measure is to replace the electric power steering pinion shaft attachment nuts.

Officials said this announcement is for U.S. vehicles included in a global recall of 106,000 vehicles by Toyota Motor Corp.

The automaker explained that if the steering wheel is repeatedly and strongly turned to the full-lock position, there is a possibility the nuts securing the pinion shaft in the steering gear box assembly may become loose.

If the vehicle is continuously operated in this condition, over time, Toyota believes the customer will gradually notice significant increased steering effort when making a left turn.

Toyota indicated its franchise dealers will install improved nuts that secure the pinion shaft at no charge to the vehicle owner. The OEM thinks the repair will take approximately four hours depending upon the dealer’s work schedule.

The automaker mentioned that owner notification letters by first class mail will be sent beginning in early July.

Meanwhile, a separate recall announced by TMS involves 34 Venza AWD and 16 Sienna AWD vehicles. Toyota said this step has been taken to replace an insufficiently heat treated front right-hand driveshaft.

The automaker insisted all of these vehicles are recently produced 2011 model year and only 38 are expected to have an insufficiently heat-treated driveshaft.

“Due to insufficient heat treatment, there is a possibility that the front right-hand driveshaft may break,” company officials noted. “If this occurs, engine power will not be transmitted to the wheels, and the vehicle will coast to a stop.”

The OEM emphasized no other Toyota or Lexus vehicles are involved in these recalls, and the driveshaft recall only involves vehicles in the U.S. and Canada.

The company intends to send owner notification letters by first class mail later this month.

Customers who seek more detailed information and answers to questions can visit www.toyota.com/recall or contact the Toyota Customer Experience Center at (800) 331-4331.

These latest recalls arrive not long after the automaker’s North American Quality Advisory Panel made a series of recommendations along with reiterating no electronic problems or software errors could have resulted in unintended acceleration in Toyota vehicles.

In a public report released last week, Toyota’s independent panel of experts suggests that the OEM loosen its tightly controlled global structure. The panel also recommended Toyota should give more autonomy to its North American operations and have a more open view regarding quality and safety issues raised by external sources.

Auto Remarketing reported more details about the panel’s findings here.