Toyota Motor Corp.’s decision Tuesday to recall nearly half a million of its hybrid vehicles, including the latest model of the popular Prius, had less to do with a safety issue involving their brakes than it did with the intense scrutiny the Japanese automaker has been under in recent weeks.

The latest recall at Toyota, affecting 437,000 of its hybrids worldwide, involves the advanced technologies contained in their computer-controlled braking systems that causes an “inconsistent feel” at times when the vehicle is travelling at low speeds on slick or bumpy surfaces.

The sensation is triggered by a 0.2-to-0.3 second lag when the vehicle shifts between its regenerative braking system to the standard hydraulic system, said Marc Stuyver, Toyota Canada’s advanced technology and powertrain manager.

The regenerative braking system is used at low speeds to both slow the vehicle and capture the energy created in the braking process to recharge the vehicle’s batteries, Mr. Stuyver said.

The problem arises when the vehicle’s anti-lock braking system causes the tire to slip slightly after a bump triggering the hydraulic system, he added.

“You will feel a change in the rate of deceleration, which in engineering terms we call a jerk,” Mr. Stuyver said. “At no point are you not braking.”

In order to fix the issue, Toyota will implement a software fix on the recalled vehicles that will decrease the sensitivity of the system which causes the hydraulic system to kick in and should eliminate the issue without compromising safety, Mr. Stuyver said.

Ford Motor Co. announced a similar issue with its Fusion and Mercury Milan hybrids last week. But unlike Toyota, Ford said it would implement a software patch as part of a “customer satisfaction program” on 17,600 vehicles, including about 1,000 in Canada, rather than a formal recall.

“We had a small number of customers report this condition,” Said Deep, Ford spokesman said. “We know so far of one complaint.”

For Toyota, the issue has been more pronounced. The regulators worldwide have received more than 200 consumer complaints about the braking systems in hybrids, including 21 in Canada, and four in the U.S. that allegedly led to accidents.

Those concerns also come at a time when the safety record of the world’s largest automaker is under increased scrutiny from regulators and consumers following the recall of more than 8 million of vehicles since November relating to the unintended acceleration of its gas pedals.

The U.S. Department of Transportation also announced a formal investigation into the braking system on the last week Prius.

As a result, Toyota announced that it would recall affected 2010 models of its Prius, Sai, Prius plug-in hybrids, and Lexus HS 250hs to implement the software fix, including nearly 3,300 Pruis and more than 300 Lexus in Canada.

Separately, it announced a recall of 7,300 of its 2010 Camrys to inspect whether a power steering hose comes in contact with a brake tube causing it to leak.

George Magliano, IHC Global Insight analyst, said there’s little doubt that the recall on the hybrids was a result of the heightened scrutiny on Toyota.

For its part, Toyota Canada maintains that the affected hybrids are safe to drive.

“This isn’t a recall because there is something wrong with the system. This is a recall because some of the customers feel unease because of that lag,” said Sandy Di Felice, Toyota Canada spokeswoman.

U.S. officials receive more than 30,000 consumer complaints a year, and launch 100 similar investigations to one launched on the Prius last week.

“The problem [Toyota has] is that it only takes one exception to disprove the rule. If your rule is that the car is perfectly safe and you have one accident, well then it’s not safe,” said Chris Piper, a management professor at the Ivey School of Business at the University of Western Ontario.

Financial Post

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