Toyota Motor Corporation (TMC) says it will cooperate with a US investigation into a previous recall of its Hilux pick-up trucks.

The US Department of Transportation’s National Highway Safety Administration (NHTSA) has launched an inquiry into whether, in 2005, TMC notified the agency of a steering relay rod safety defect within five business days of learning of the problem, as mandated in American law.

A statement from NHTSA said: “In 2004, Toyota conducted a recall in Japan for Hilux trucks with steering relay rods prone to fatiguing, cracking and possibly breaking, causing the vehicle to lose steering control.

“At that time, Toyota informed NHTSA that the safety defect was isolated to vehicles in Japan and that the company had not received similar field information within the US. In 2005, however, Toyota informed NHTSA that the steering relay rod defect was present in several models sold in the US and conducted a recall.”

But the NHTSA said it was alerted to a number of complaints filed with Toyota by US consumers prior to the 2004 Hilux recall in Japan. As a result, the safety watchdog has decided to open an investigation into whether Toyota met its legal obligation to conduct “a timely recall” of vehicles with the defect in the US.

“Safety is our number one priority and we take our responsibility to protect US consumers seriously,” said US transportation secretary Ray LaHood. “With new assurances from Toyota about their efforts to improve safety, I hope for their cooperation in getting to the bottom of what happened.”

The NHTSA added it had taken “swift action” since it received copies of the complaints last Friday (7 May).

“Our team is now working to obtain documents and information from Toyota to find out whether the manufacturer notified NHTSA within five business days of discovering a safety defect in US vehicles,” said NHTSA administrator David Strickland.

The automaker confirmed it would work with the NHTSA: “Toyota has received and is reviewing the information request from NHTSA and will cooperate with the agency’s investigation,” it said in a statement.