Mixing Sensor Ground and 5v Supply

So I have a Link razor PDM and Link G4x plugin and both will end up with sensors attached to them. How bad of an idea would it be to run say all 5v supply off the PDM but still send signal back to both the PDM and the ECU. It would certainly simplify wiring as i would only have to run a single 5v supply and ground through into the engine bay and wouldnt need to keep track of which is which.

The sensor supply and sensor ground pairs are closely monitored and regulated to output a potential difference of 5V, and the sensor signal reading will be in reference to said sensor ground. Mixing up that way is likely to give you erroneous readings due to slight offsets in sensor supply or sensor ground. I would avoid it.

Agree -- voltage supply and ground returns need to be to the same device measuring the voltage.

Just in case you needed a third person to convice you, I agree with Christos and David.

I should have been more clear in that i would source both supply and ground from the same device and in that context the differential voltage of 5v would be retained. I do sorta agree that its kind of a bad idea and a bit lazy. Might be something to test at some point just to see how much of a difference it makes

sɹǝʇʇɐW ʎɔɐɹnɔɔ∀

Hey Edward, yes that was clear from your first post that you'd provide both sensor power and sensor ground from the same device, however imagine this:

You supply sensor +5V and sensor 0V to a sensor from your PDU, and then read the output of the sensor from your ECU. The reading in the ECU would be with reference to the sensor ground of the ECU, which can be offset to the sensor ground of the PDU, which supplies power to the sensor. So if those grounds have an e.g. 0.01V potential difference, this would be reflected onto your sensor output reading.