Dumb Question about Can Bus System.

[jorgensensc]

So I'm trying to figure out something regarding My fuel System. My fuel level sender needs to send the signal (ohms) 240-33 range and also a 5 volt reference to the ecm for my gauges to work. Can I use a regular aftermarket sender (240-33 ohms) and use the ground wire as the 5 volt reference? I'm confused on exactly what the 5 volt reference is and what it is used for. I've got a reasonable fuel system figured out, I'm just having difficulty with the fuel sending system. I must use the Can Bus system for my gauges. Any ideas or help?

[68GMCCustom]

I'm running my electric fuel gauge independent of the efi system. As I recall mines a 0-90ohm one though.

otherwise....not sure about how to pull off the cab buss....if its not there!
I'm guessing on the sender but see no reason another manufacturer's with the same specs wouldn't work. Not sure about 5v.

[clinebarger]

The sender wire from the PCM to Fuel gauge will read 5vdc when unhooked.....Not really a Reference feed. The other side of the sender goes to ground.

I'm guessing your working on GMT800 (99-07) electronics not GMT900 (07.5 & up)??

[jorgensensc]

Thanks for the replies.

Clinebarger,
It is actually an '08 escalade ECM. That's why I'm having difficulty. On the wiring schematic for the fuel sender it shows the fuel level wire and a 5 volt reference wire. But all of the aftermarket fuel senders that I want to use only have the fuel level wire and the sender ground wire. No 5 volt reference.
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[dayj1]

Originally Posted by jorgensensc

So I'm trying to figure out something regarding My fuel System. My fuel level sender needs to send the signal (ohms) 240-33 range and also a 5 volt reference to the ecm for my gauges to work. Can I use a regular aftermarket sender (240-33 ohms) and use the ground wire as the 5 volt reference? I'm confused on exactly what the 5 volt reference is and what it is used for. I've got a reasonable fuel system figured out, I'm just having difficulty with the fuel sending system. I must use the Can Bus system for my gauges. Any ideas or help?

Maybe I'm looking at the wrong schematic, but the one I've got for an '08 Escalade shows ECM connector C1 (black connector) pin 31 as a tan/black wire (low reference) to pin B of the fuel pump module connector. ECM connector C1 pin 16 as a purple wire (fuel level signal) to pin C for the fuel pump module.

So, you would hook the ground wire of your 240-33 ohm aftermarket sender to pin 31 and the other sender wire to pin 16. I don't see a 5v reference in relation to the fuel level. Do you have a link to the schematic that you're using?

[jorgensensc]

Originally Posted by dayj1

Maybe I'm looking at the wrong schematic, but the one I've got for an '08 Escalade shows ECM connector C1 (black connector) pin 31 as a tan/black wire (low reference) to pin B of the fuel pump module connector. ECM connector C1 pin 16 as a purple wire (fuel level signal) to pin C for the fuel pump module.

So, you would hook the ground wire of your 240-33 ohm aftermarket sender to pin 31 and the other sender wire to pin 16. I don't see a 5v reference in relation to the fuel level. Do you have a link to the schematic that you're using?

Thank you! Funny You say that!! I was re looking at the wiring schematic and noticed the same things in regard to low reference wire. you are correct on the pin out too. So with that said, (and after looking at the low reference wire for the fuel pump also) and applying some very basic electronic knowledge, it seems that low reference is the same as ground. Does that seam right to you? If so it makes my life a whole lot easier. Why didn't they just say ground instead of low reference?!

[jorgensensc]

And Just read this:http://ls1tech.com/forums/pcm-diagno...vs-ground.html

Explains everything! Makes my life a whole lot easier!!

[jorgensensc]

On a side note, can you adjust the ohms in the ecm? For instance, can I make the computer read 0-90 ohms as empty to full vs 230-33 empty to full?