Mustang Parts
   Carrying Saleen wheels and Bullitt wheels.

Saturday, September 17, 2005

Details About Volvo ETM Failures

Don Wilson, a retired metallurgical engineer, has posted a detailed analysis of the failures of 1999-2001 Volvo ETMs (Electronic Throttle Modules) at his web site, VexedVolvo. He has photos of a disassembled unit, clearly showing how the resistance film potentiometers wore through, and the wiper contacts picked up debris.

Image courtesy of

Don's conclusion:
The construction of this potentiometer is obviously not suitable for the application. Considering that in the life of the car there will be multiple millions of cycles of the throttle, the action of the hard metallic finger tips riding on the soft thick film carbon resistor element is a designed-in shortcoming that will result in an estimated 100% or more, failure rate in the life of the Volvo automobile.
I am glad that I drive a throttle-by-cable car!

(HT: Autoblog)


The Angry Engineer said...

Ah, a wear-through failure of conductive ink. I'm shocked.

Ray said...

Looks like one of my many old, worn (TPS) Throttle Position Switches which made the car run, shall we say, reluctantly.

Ray said...

Make that Throttle Position Sensor...

Anonymous said...

Co-Molded conductive plastic Pots,
such as those made by JDK of California last for millions of rotations and resist "dither" far better than cheap film pots.
Problem is, they cost significantly more. A few bucks never seems to bother Lexus does it?

Anonymous said...

does this affect deisel cars 2002

Anonymous said...