Toyota calls "grossly inaccurate" a report on CNN.

Toyota has called “grossly inaccurate” a news report on CNN that charges the Japanese maker with covering up a memo that could reveal additional causes for so-called “unintended acceleration.”

The Japanese giant recalled millions of vehicles in late 2009 and early 2010 due to a series of issues that could cause its vehicles to unexpectedly race out of control.  But Toyota insisted that the problems did not include defective electronic control systems – a conclusion echoed by a pair of studies authorized by U.S. federal safety regulators.

Nonetheless, the latest report by CNN, which cites internal documents, could prove problematic considering the maker is facing numerous suits by owners who claim they experienced unintended acceleration.  If the network’s report proves true it could also pose a problem since the National Highway Traffic Safety Administration has already imposed record fines on Toyota for failing to properly act when it discovered prior safety-related problems.

In its report on Thursday night, CNN quoted a 2006 internal memo covering testing of various vehicles including the Lexus LS460.  The maker’s engineers noted, “”The cruise control activates by itself at full throttle when the accelerator pedal position sensor is abnormal.”

According to the confidential document, written in Japanese and translated into English, a “fail-safe overhaul” was needed on one model then known as the 180L and later marketed as the Toyota Tundra.

If that’s correct it would mark a significant shift in the unintended acceleration story.  The very first Toyota recall involved loose carpets that could jam a vehicle’s accelerator.  The second recall covered potentially sticky accelerator pedals.  But Toyota has consistently and repeatedly denied that it has had any problems with its electronic control systems.  And that position was echoed in studies by both NASA and the National Academy of Sciences – both commissioned in 2010 by NHTSA, the federal automotive safety regulator.

The most recent NAS study largely pointed to driver error – but it did, however, leave open the slight possibility that not all problems were uncovered.  And most of the legal challenges Toyota faces focus on claims of electronic glitches.

In its Thursday night report, CNN quoted Michael Pecht, a mechanical engineering professor at the University of Maryland, arguing that based on the confidential Toyota memo, “This looks like an example of electronics causing a car to suddenly accelerate.”

Toyota faced the first in a series of record fines for failing to disclose the sticky accelerator problem to NHTSA in a timely manner.

For its part, Toyota insisted to CNN it did not share the newly unearthed confidential memo because it “had nothing to do with unintended acceleration, or a defect, or a safety flaw of any kind.”

Following the airing of the broadcast, the Japanese maker charged that, “In the face of overwhelming scientific evidence to the contrary, CNN has irresponsibly aired a grossly inaccurate segment on Anderson Cooper 360 that attempts to resurrect the discredited, scientifically unproven allegation that there is a hidden defect in Toyota’s electronic throttle control system that can cause unintended acceleration.”

Significantly, since the issue of unintended acceleration in Toyota vehicles first made headlines the number of reports of such problems has steadily declined.  But they haven’t vanished entirely, and 331 incidents were reported to NHTSA in 2011.  Considering the most recent study by the NAS left open the possibility that it could be hard to totally rule out unknown electronic problems it remains to be seen if the memo CNN quoted will force federal regulators to reexamine the issue.