I'm pretty sure that is the case.Just browsed the schematic; that orange wire is the ground return for all sensors, that we agree on. If that wire was not making to the ECU plug then a whole load of other sensors wouldn't work and the car would -maybe- not even run at all.
The ECU feeds a positive voltage out on the Violet/Yellow where it goes to the temperature sensor and the temp gauge.What the OP needs to do is verify that the Violet/Yellow wire is making it to the ECU [pin 38]. Easiest way is to measure [with the ohmmeter setting] between pins 38 and 91 of the ECM connector. It should read SOME resistance, -the sensor's resistance. If open circuit THEN follow wires.
... i had a mechanic come out and look at it and tested the engine coolant temp sensor to find out that was giving off almost 3x the power it need. so i replaced that, also tried to replace the clip for it with new wires and no luck. the mechanic told me i need to trace back the wires to the harness and see where it’s burnt out at and go from there.