Thanks a lot Adam, finally we have got it to work. The problem was with the script that send the messages with CAN bus to the ECU. Until a target position was not selected, the script wasn't sending any message, so the ECU detected that.
Finally, we would like to know if there is a way to change the Electronic Throttle Mode by sending a CAN message, or, how could it be changed automatically, not by hand?
Thanks again.