Been fighting the fuel gauge readings for quite sometime now....thought it was better, but no.
So I was getting ready to put a resistor in parallel with the fuel level sensor, but I measured the resistance across the sensor (purple and black) wires with the connector apart....and I get 35 ohms. I have driven 269 miles with 22 mpg....so I have used almost 12 gallons....which makes the 35 ohms very close.

So the problem is not the fuel level sensor, but the Body Control Module where the fuel level sensor goes into.

Anyone have any details, schematics or information on the fuel level input into the BCM.....anything at all??????

Is the BCM located behind the stereo? Anyone ever work on one of these?

I really would like to have a fuel gague I can use.

 

Went ahead and put about 190 ohms in parallal with the fuel level sensor and this dropped the gague down by two bars. So...now I have more fuel than the gauge shows....which is ALOT better than the other way around.

Filled tank this morning...drove 26 miles to work and gauge was down one bar already.

As stated above, better to have more fuel than less fuel showing on the gauge.

If anyone hears of someone tearing into a BCM.....could you point them out for me. I would sure like to know what the fuel level input circuit looks like.

 

90 ohms = 3.5 volts input to the CCM. Gauge should show Full
45 ohms = 1.7 volts input to the CCM. Gauge should show 1/2 Full
0 ohms = 0 volts input to the CCM. Gauge should show Empty


Did you verify if the CCM is processing the input from the Fuel Level Sender correctly?

You can use a Tech 1 or short pin 12 to pin 4 on the Diagnostic connector.
Turn the ignition On.
After the CCM cycles thru the different modules and stops, you select Mode 1.2 (Display CCM Data)

Press the Trip/ODO button until 1.2 is displayed in the Trip Monitor area.

Press the ENG/MET button until 01 is displayed in the first two digits of the odometer.

The data value is displayed in the last three digits of the
odometer.

Example: Last 3 digits displayed are 012 would represent 1.2 gallons.

If the correct voltage/resistance values are correct
from the sender and the fuel gauge display is wrong
the problem is in the CCM.

 

I did not know I could get the CCM readout like that.
I will give that a try.

I filled the tank up with the resistor is parallel and after about 30 miles the level dropped one bar.
Drove another 30 miles and dropped another bar.

Now I have about 150 miles driven and the level appears to be stuck at thee bars down or one bar above half.

Looks like the CCM is not processing the input correctly...hopefully just due to dirty connector pins or something. Will work on it this weekend (again).

Thanks for the information.

 

I've got a similar problem with my fuel gauge.

Last Thursday the gauge showed that I've got 20 miles left in the thank and on my way to the gas station still on 20 after a 1/4 of a mile I ran dry.
Now I was reading this thread and started thinking. So if or should I say when I run out of gas if I measure the pink and black wires coming from the tank it should read 0 ohms right?
So if I want the gauge to read 0 when it's empty I have to put in a resistor to compensate?

Where would be the best place to put the resistor (I figure around the area where the wires connector is by the fuel tank)?
And since I haven't taken the whole car apart where can I find this connector and what's the best way of accessing it?

Thank you for the info and best regards

 

Me to.

But with all working pretty good with my vette I'm not about to explore the CCM as much as I would like to. Not to say the effort in getting it out of the car, disturbing who knows what and hoping all the pins seat correctly in the connectors.

I know a guy that runs a big vette junk yard here and tried to get some defective CCMs and PCMs. No can do, he says it all has value so I could not get one for free.

You would think GM could release the documentation for these items since they don’t even support them anymore. They keep it under wraps like it's government documents for national security.

I posted my how to fix the fuel gauge with the resistor thread back in 06. But was doing that repair years before that on other cars. The kicker is my fuel gauge is not working as well as it once was when I put I my original 180 ohm resistor. Something again has changed to slide me back to the area I started in and the resistor is still good.

FYI: http://forums.corvetteforum.com/c4-t...-and-more.html

I thought about making a complete resistance measurement from the CCM. But that involves either removing the connector off the CCM (but not doing that!) or cutting the correct wire back to the sending unit for the measurement. Just have not been motivated to dig into that effort yet.