Also overlooked here is to use self diagnostics to determine that the ON/OFF switch is activated before the display starts to indicate the 0-15 position steps.
As Hans says the accelerator pot is very reliable and in our expierience error code 51 can be solved by simply rotating the pot on the adjustment slots.
This is ONLY to be used to report flooding, spam, advertising and problematic (harassing, abusive or crude) posts.