I like to know where the actual wires from the ECU for pin 1 and 19 for grounding the ECU are attached to the chassis. When measuring these two points towards the chassis of the car I get a 0.3-0.4Volts differents so the earth connections are not perfect.

Who can tell me where in the car these wires from the harness are attached? It's a Ford Sierra Cosworth 4x4.