I have a problem with my fiat siena black smoke and rough motor running all the test and trying and cleaning point to the idle sensor in the throttle body not working if i unplug the cable the engine is hunting (there was a tread here about that) but i have been advised by an (expert) that before i go and buy a new throttle body I should get an ODB tool read the errors than clear the errors and that my csolve the problem, while i think gettin an ODB tool is a good idea, is it possible that clearing the error in the system fix the problems? any experience there?

Clearing the errors isn't going to fix the problem. However, clearing the errors will get rid of any "historic" errors, so that when the system detects new errors you will know for sure what is currently wrong, and not what the ECU thought was wrong at some point 6, 9, 12 months ago.

What model year is your Siena?
Until about 2002 the Palio/Siena range used the Fiat 3 pin connector under the hood, in the engine bay.
Without special adapters, hardly impossible to read.
After about 2002, the WCP 178 range got the 16 pin connector inside the car, near the fusebox, easier to read with inexpensive code readers...