i had the fuel pump replaced recently by a lingenfelter pump on my 99 c5. a few days later the low fuel level warning came on as well as the red and orange lights and the gauge showed zero. i put some more fuel in there, nothing changed. i brought it back to the mechanic and he said it was not the left sender because he checked with a potentiometer. so i filled her up and expected the gauge to come to life because of some reading from the right sensor, but it didnt.

this seems to be different from all the other threads, it doesnt go on and off.

so i checked myself. there is 5v on the left middle pin of the connector from the pump. there is 0.5 ohms from the right middle pin to ground. i hokked up a 100 ohm resistor and a 220 ohm potentiometer and was able to vary the voltage between 1.5v and 3v. nothing changed with ignition on (i hope engine doesnt have to be running). there is 180 ohms between the middle pins on the pump.

weird, the two circuits from the sensors seem to be separate, going to pins 54/c2 and 73/c2 respectively and died at the same time? or did the mechanic somehow fry them when testing?

so is the issue within the ecu now and i would need to replace it?

interestingly im not getting any codes (exept for maf and crank sensor). im not very proficient with efilive, but i see p0461-3 set to 1 trip (sensor 1) and p1431-3 to non reported (sensor 2), where in the stock tune all was set to non emissions. all of them are set to no mil as they wrre in the original tune.

can anybody make any sence out of this?

 

If you have no codes it is most likely a stuck level sensor or a fouled one. Have you heard of using Techron to help remove sulfur deposits?

I really doubt it is the PCM.





Fuel Senders


Mr. Sam

 

+1 for Techron. My old car (98 Coupe) had the same issue. It doesn't matter how much gas it had, intermittently the gauge would drop to zero and the dash would light up like Christmas! I did some research, and found that Techron was the magic juice to fix the gauge! Now, if you have an electrical problem, that's something else entirely. But try a bottle (or two) of techron in your tank see how it does!

 

2 for Techron! Fixed my 2001quickly.

 

o.k., the forum is full of techron threads. we dont have techron over here. neither do we have chevron. anyways, this is not the issue, i think.

first my impression was that both sensors wouldnt quit at the same time after 15 years of service. well, they dont have to, it seems. if the rs >0.8v and ls < 2.3v the gauge will show empty and you get the low fuel message, meaning right tank is not empty when left tank is less than full. thats what i read anyway.

further research:

- 1997-2003 are without the FFS system (whatever that is), meaning the tanks will equalise when engine is not running

- sensor range is 40 - 240 ohms (full)

- voltage goes from full to empty: 2.5v to 0.7v on right tank and then from 2.5v to 0.7v on left tank

- info goes from sensors to pcm to bcm (body controll module) to gauges

somebody correct me if this is wrong.

the 180 ohms are consistent with 3/4 full. i was able to logg the sensor output voltages. they are 1.9v left and 1.7v right at start up and 2.2v left and 1.3v right after driving. all consisten with the above. so i conclude the sensors work just fine.

questions:

- where do i find a plug to measure the right sensor independent of logging?

- where is the bcm?

- if the bcm controlls the gauges, does it controll the low fuel message also?

- does the bcm send any codes?

if not, that would explain no codes being there. so the problem is between pcm and bcm, or the bcm, right?

well, what do i do next?

 

im still struggling with this.

to make it short: both sensors work, fuel gauge is dead, "gauges" light is on, i have no codes?

ideas?

 

Hello, you are correct, both left and right fuel level senders are independent reports to the PCM, as this reporting ensures that the fuel is transferring from the right fuel tank to the left fuel tank (at the proper transfer rate). Check out my posting (number 3) in the thread ling below for a 1999 model year.
https://www.corvetteforum.com/forums...nder-says.html

Kevin

 

This was a great post and enjoyed all your comments. Everyone had some good solutions.

 

Techron is your friend. Auto Zone is running a special right now. I just bought 10.

 

I've used Sea Foam on my 02 several times. Works as good as Techron.

 

You might check your fuel gauge in the bezel. I had similar problem. Thought it might be the fuel sensor. Found out it was the fuel bezel gauge. Replaced the with NOS . Works fine now.

 

interesting. is there a way to check the gauge?

 

Yeah pull the dash. :banghead

 

is there a pinout of the bcm somewhere? any info on the voltage that comes out of there?

(if i have to pull the dash i just let it be.)

 

You have to get a wiring diagram. Not sure. I took mine to the steelership and they said it was the fuel gauge . They changed the the whole assembly. Plus I had them change all oils and spark plugs and wires. Minor tune up