Does anyone know the ohm range of the fuel level float in the C5. Older GM products were 0 ohms empty and 90 ohms full. But I am having a hard time finding out what the range is for a 2001 C5.
Thanks for any help.
P.S. I don't have access to a shop manual. I think the ohm range would be shown in the schematics section.

 

The PCM supplies a 5 volt signal to each fuel sender. The senders are a variable resistor and alter the resistance based on the float angle. An empty tank returns about 0.7 volts, a full tank returns about 2.5 volts.

The PCM takes these two voltages and averages them to get a single "level" that it then reports to the IPC.

 

Thanks Stephen. As far as how the fuel level is determined I was given a little different explanation. According to a mechanic I know there are the two fuel tanks (left, driver's & right passenger's side). There is a pump in the right side that moves fuel to the left tank to maintain the levels in both tanks the same. Only the left tank actually provides a fuel level indication to the system. This works fine assuming that the level of fuel in both tanks is the sme.
Does this sound like a correct scenario to you?
ttt

 

Nope .... here is how it works.

First, each tank has its own fuel sender that reports the fuel level to the PCM.

Second, when you fill the car, the left tank fills first, then a large cross-over pipe that connects the tops of the two tanks feeds fuel to the right tank until it is also full.

There is a "regular" electric fuel pump that drains the left tank and feeds the pressurized fuel to the injector rails. Just after the fuel leaves the pump, there is a small fuel line that branches off to the right tank, where the pressurized fuel runs through a "jet siphon" pump that picks up fuel and moves it across to the left tank using another line.

So, after you have filled both tanks, and start driving, what happens is the level in the right tank drops as you consume fuel and the left tank stays full. Once the right tank is empty, the left tank now drains down.

The PCM actually has "logic" in it that can help it spot problems. For example, let's say you fill the car, and the fuel is dirty and shortly after you start driving the right tank jet siphon pump clogs. As you drive the left tank will drain, but the right will stay full. Once the PCM sees the left tank draining before the right, it will set a DTC and issue the LOW FUEL message on the DIC and drop the fuel gauge to empty. Another example is let's say you are driving along and the right fuel sender "hangs up" before the right tank is empty. Again, when the PCM sees the left tank is now draining (because the right tank really has emptied) but the right fuel sensor (incorrectly) reports fuel still in the right tank ... Bingo ... a DTC sets .... etc.

And that's why so many people have complaints about "sticky" fuel senders ... either sender sticking will cause a DTC ... and any problems with the right tank siphon pump will also cause a DTC.

Hope that helps ...

 

Thanks again. That is a great explanation. I really appreciate your response.