VW Polo

Hello, I have a problem in a VW Polo 1.6 Mi, I have a customer who has the motor problem step by step varea the march and accelerate changes the step by step, and connect the scanner and tells me that I have a short to mass, I look at the tension of the 2 pairs of 12 volt and cut the current I measure the continuity from the ECU card to the step by step and this is fine but the tension disappears

friend. From what I read, there may be two problems. 1º The wiring from the ECU to the sensor is internally damaged (and you go to Maza) 2nd (and more serious) the ECU is in short sporadic at the exit to the sensor ... you have to take it out and send it to repair or replace it.- I hope it is helpful.-