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Tin whiskers in accelerator pedal mechanisms -> MIL or drivability problems

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cwerdna

Well-Known Member
Jul 11, 2012
5,135
4,255
SF Bay Area, CA
Related to Another NHSTA Unintended Acceleration Complaint...

Tin whiskers in accelerator pedal mechanisms have apparently caused problems for those w/Gen 1 (01-03) Priuses aka NHW11 and Camrys, in the past.

See Accelerator Rebuild - lessons learned | PriusChat. Especially interesting were slides 8 and 13 of http://web.archive.org/web/20130601050821/http://nepp.nasa.gov/whisker/reference/tech_papers/2011-NASA-GSFC-whisker-failure-app-sensor.pdf.

From slide 8:
Extract from NASA Findings
•Vehicle testing of a MY 2005 Toyota Camry demonstrated that a 248 ohm short between VPA1 and VPA2 results in different vehicle responses depending on the sequence of operations following the fault
–If the pedal is depressed quickly, then throttle is limited to 15 degrees
–If the pedal is depressed slowly, then throttle can jump to 15 degrees, and further pedal application can achieve wide open throttle
•In all cases, releasing the accelerator pedal closes the throttle, and brakes are fully operational
–Although the vehicle would operate, we did not consider it to be driveable
From slide 13:
Source of Accelerator Pedal Assembly Provided to NASA Metal Whisker Teamhttp://www-odi.nhtsa.dot.gov/complaints/
•Make : TOYOTA Model : CAMRY Year : 2003
•Manufacturer : TOYOTA MOTOR CORPORATION Crash : No
•Fire : NoNumber of Injuries: 0
•ODI ID Number : 10304368 Number of Deaths: 0
•Date of Failure: November 11, 2009
•Component: VEHICLE SPEED CONTROL:ACCELERATOR PEDAL
•Failure Mileage:81,957 (information courtesy of DOT)
•Summary: I HAVE A 2003 CAMRY. ON NOV. 8, 2009 I HAD A VERY BIG PROBLEM WITH THE ACCELERATOR. WHEN STEPPING ON THE GAS PEDAL I COULDN'T GET ANY GAS, AND THEN THE CAR WOULD JERK FORWARD AT A RAPID RATE SO THAT I HAD TO APPLY THE BRAKES. IT WAS TOTALLY UNDRIVABLE. THE MECHANIC REPLACED THE GAS PEDAL ASSEMBLY, AND I HAVE THE OLD PART IN MY POSSESSION. THE PART WAS $428.01 PLUS THE LABOR COST. MY OLD CAMRY I DROVE FOR 12 YEARS WITHOUT ANY PROBLEMS. I FEEL THE PART WAS DEFECTIVE AND THAT TOYOTA SHOULD REIMBURSE ME FOR THE COST OF REPLACEMENT. WOULD YOUR AGENCY PLEASE LOOK INTO THIS FOR ME?
9/14/20115th International Tin Whisker Symposium
13
NOTE: NHTSA report states warranty analyses identified at least two additional failures due to tin whiskers in similarly designed APP sensors

On the Gen 2 Prius (NHW20, aka 04-09 model year), AFAIK, their going to Hall effect sensors eliminated the issue w/the NHW11.
 
Tin whiskers is a widespread problem caused by using no-lead solder (RoHS - Reduction of Hazardous Materials has been imposed on the electronics industry by EU and I believe also by California). The problem is that under certain conditions if the solder joint has some "stress" it will literally grow whiskers of tin that can short out to nearby circuits.

In this case it doesn't sound like the car was really dangerous; rather it was not drivable. I've experienced a similar drivability problem with a gas car where there was a problem with the intake manifold - car speed was all over the map. Very annoying to say the least but there was no problem controlling the car.