In the latest indication of struggling with vehicle problems despite works to overhaul quality control, Toyota is recalling nearly half a million cars for problems that can cause the steering wheel to lock up.

The recall declared yesterday affects 412,000 vehicles and is Toyota's largest since announcing it would fix 600,000 Sienna minivans over rusting spare tyre holders in April. Of the total, 373,000 are Avalon sedans and 39,000 are Lexus LX 470 SUVs.

Toyota has been entangled in its recall crisis since October, when it issued a recall of 5.3 million cars and trucks to fix floor mats that can trap pedals and cause accidental acceleration. A series have followed, from sticky gas pedals to braking problems with the Prius hybrid to rusting frames involving the Tacoma pickup.

Thursday's news blows up the size of Toyota's recalls to about 9.5 million cars and trucks in the US since October, with some affecting units as old as the 1998 model. As tracked by Wards AutoInfoBank, the figure means about 39 per cent of the 24.1 million vehicles Toyota has sold in the US since 1998.

"I don't think it's going to end anytime quickly or easily," said George Magliano, auto analyst with the consulting firm IHS-Global Insight, on the Toyota's recalls.

"Toyota had this big run of growth. The more they grew volume and market share, the more this (quality) system started to develop cracks."

Toyota has been working to improve QC after being criticised for its slow response to vehicle flaws. It has been employing thousands of engineers to check for problems and appointing chief quality officers in its major regions.

"Toyota is continuing to work diligently to address safety issues wherever they arise and to strengthen our global quality assurance operations," said Steve St. Angelo, Toyota chief quality officer for North America.