Veronica Merryfield wrote:
> Whilst the sensor, TPS or otherwise, may only be a pot or other resistive 
> element, there is a lot that can be done at the raw signal processing 
> stage that can identify a number of fault modes, including open circuit 
> and short circuit (both usually arranged not to be co-incident with full 
> open and full closed peddle position), rate of rise or fall of signal and 
> so on. Sensors and wiring are known to be weak points in the system and 
> handled accordingly. I very much doubt Toyota do not have this sort of 
> thing in place. 15 years ago when I last worked in that industry, racing 
> and commercial, these sorts of signal integrity tests were common place. <


Besides checking for shorts or opens, the ECU also check the TPS voltage at 
idle. These three generic diagnostic trouble codes describe the three 
possible conditions:

P0121 Throttle/Pedal Position Sensor/Switch A Circuit Range/Performance
P0122 Throttle/Pedal Position Sensor/Switch A Circuit Low
P0123 Throttle/Pedal Position Sensor/Switch A Circuit High

Vitaliy 

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