Edward
I wasn't refering to the bad spot as being an "open circuit". I was leaning more toward it being a "hotspot", causing the voltage to jump to full range instead.
Maybe I should have clarified that instead of just throwing out that rather broad suggestion. :o)
Sorry about that
what type of controller is fitted? very few controllers will have high speed as the 'open circuit failure' of the pedal position pot.
I think it is more likely the linkage to the pot slips, I have seen some that have a piece of hose to connect the pot shaft to the linkage, and the hose slip, but even that will eventually show a code in an ev100 (or newer) system.
Faulty accelerator?
A bad spot in the pot wiper may cause a sudden change in the signal to the controller causing it to go into full speed.