Fuel Gauge and PCM fuel level input

[Rhino]

I've got what I hope to be a simple question about modern electronic sending units. I'm working with a late 4th Gen PCM (12200411) which I believe expects a 33-270 ohm sensor.
In this scenario, what is the PCM actually sensing? Is it truly measuring resistance of the circuit or is it only interested in voltage drop across the sensor?



I'm trying to determine if it's safe to tap into the same sensor to drive both my PCM fuel level in addition to aftermarket gauges.

[Rhino]

From what I'm reading it's quite likely that the PCM is simply measuring voltage drop across the sensor. That being the case it should be safe to drive both the fuel gauge and PCM fuel level input off the same sending unit (as long as they're both rated for the same resistance range).

[nokones]

If you connect the aftermarket gauge to the existing circuit and the OEM indicator changes than it is likely that you cannot run the second gauge in conjunction with the original gauge because of the additional load on the circuit thus, changing the load resistance. My bet, the original gauge will show a different indication when the second gauge is connected.

[Rhino]

Good point. I'll have to check that once I get everything wired up. I was trying to determine whether or not to order a sending unit with a set of gauges. I'm going to roll the dice and see how it goes.

My assumption is that both the PCM and gauges are quality products that have enough input resistance that any shift in circuit resistance should be minimized.