Toyota has recalled around 8.5 million vehicles worldwide and admits the company's safety standards have slipped.
"Toyota has, for the past few years, been expanding its business rapidly. Quite frankly, I fear the pace of which we have grown may have been too quick," Toyoda said, reiterating a statement the company released on Tuesday.
"I would like to point out here that Toyota's priority has traditionally been the following: first - safety, second - quality, third - volume. These priorities became confused."
He offered his "personal committment" to restore customers' trust in the company by working "vigorously and unceasingly" to correct problems with the recalled cars.
Al Jazeera's John Terrett, reporting from Washington, said Toyoda's decision to appear before congress was highly unusual, as the hearings are usually held for US politicians or captains of industry based in the country.
"It is quite extraordinary and a moment of history to see the head of a Japanese corporation coming all the way from Tokyo ... to be grilled by politicians of another country's political system about the faults that his company allegedly has," he said.
His apology came after the head of Toyota's US operations said he could not guarantee that fixes being applied to millions of cars would completely eliminate all potential problems.
Speaking in Washington before a separate congressional panel on Tuesday, Jim Lentz said about 70 per cent of complaints related to unintended acceleration remained unexplained.
Speaking to reporters later, Lentz said many lessons had been learned from the crisis and big changes were planned for the firm.
Analyst discusses the influence of US politics on the Toyota recall saga
"We are going to be a much more transparent company in the future," he said.
"So if someone in the company doesn't want to be transparent or if someone in the past has concealed things then, yeah, maybe they have to go."
Also on Tuesday, on the first day of congressional hearings into the Toyota recalls, the driver of a Toyota Lexus involved in a 2006 incident where her car apparently accelerated to 160kph gave an emotional account of the incident.
Holding back tears Rhonda Smith recalled placing what she thought would be her last telephone call to her husband as her Lexus ripped forward on a highway.
"I knew he could not help me, but I wanted to hear his voice one more time," she said.
Smith accused Toyota and the US National Highway Traffic Safety Administration (NHTSA) of ignoring her belief that the car's electronics were to blame.
"Shame on you, Toyota, for being so greedy. And shame on you, NHTSA, for not doing your job," she told a panel of the House Energy and Commerce Committee.
Speaking to the same panel, Ray LaHood, the US Transportation Secretary told lawmakers that he had found Toyota's Japanese executives "safety-deaf" when he took office last year but that he believed the company had since charted a different course.
|Acceleration problems with Toyota cars have been linked to at least five deaths [EPA]
Nonetheless, he said, his department would conduct a "complete review" of the electronics on Toyota vehicles.
This week's congressional hearings come as Toyota faces a subpoena for dozens of internal company documents from a US federal grand jury investigating whether there is sufficient evidence for criminal charges related to the defects.
Unintended acceleration problems with Toyota vehicles have been linked to at least five US deaths, with another 29 fatal crashes being examined by US authorities.
In Japan, meanwhile, politicians expressed growing worries that the impact of the recalls and the investigations into Toyota could have a lasting impact on Japan's image abroad and its ability to pull its economy out of recession.
"It's a matter of safety and quality, so it is important for them to gain the understanding of the American people and work to rebuild trust," Hirofumi Hirano, Japan's Chief Cabinet Secretary, told a news conference on Tuesday.
"The fact that there was a fault in quality must be accepted gravely."