WASHINGTON -- The sudden unintended acceleration problems in Toyota's vehicles have touched off a firestorm of controversy over the cause. Now, a professor of automotive technology at Southern Illinois University has entered the fray, testifying before Congress that the trouble locating the problem's source could stem from a missing defect code in the affected fleet's diagnostic computer.

In testimony before a house subcommittee Tuesday, David W. Gilbert, a Ph.D. with almost 30 years experience in automotive diagnostics and troubleshooting, said his initial investigation has found problems with the "integrity and consistency" of Toyota's electronic control modules to detect potential throttle malfunctions.

Specifically, Prof. Gilbert disputed the notion that every defect would necessarily have an associated code. The "absence of a stored diagnostic trouble code in the vehicle’s computer is no guarantee that a problem does not exist."

Using a 2010 Toyota Tundra, Prof. Gilbert discovered electrical circuit faults could indeed be introduced into the electronic throttle control system without setting a diagnostic trouble code. "Without a diagnostic trouble code set, the vehicle computer will not logically enter into a fail‐safe mode of operation. ... Since the vehicle computer will only react to defective sensor inputs outside of the range of programmed limitations if the circuit is not defective; it must be good."

In other words, because a code did not exist for the sensor to inform the on-board computer of a problem, when a short occurred the computer did not recognize the problem, and therefore it took no steps to mitigate it. And absent the code, no defect was entered into the database for post-incident tracking. Prof. Gilbert further determined that electronic control module malfunction detection strategies were not sufficient to identify all types of fundamental APP sensor and/or circuit malfunctions. "Some types of electronic throttle control circuit malfunctions were detectable by the ECM, and some were not," he testified. "Most importantly, the Toyota detection strategies were unable to identify malfunctions of the APP sensor signal inputs to the ECM." ( Dr Griffin's test at his university test track is on video here.)

 

Commenting on Prof. Gilbert's testimony, one reliability expert told CIRCUITS ASSEMBLY this could be the smoking gun. Toyota has yet to respond publicly to Prof. Gilbert's findings.