Using the V7 scantool, log the pid GM.FUELREM and see what it says (does it look close to how much fuel is in the tanks...?)...?
Using the V7 scantool, log the pid GM.FUELREM and see what it says (does it look close to how much fuel is in the tanks...?)...?
From the 1999 GM SM see attached... the info doesn't seem to be very good (and requires scantool that can read from IPC).
If you have the 97-2003 C5, Replacing the fuel pump, located at the left wheel wheel well, is relatively easy, the 2004 had a different type of fuel pump system and is more complex in fixing. IF you are going to replace the pump, I would also replace the fuel filter which is located just in front of the left side fuel tank.
thanks joe. so it looks like you replace the ipc if there is a problem. it seems the ipc is no longer available, the cheapest used one i see is around usd 500, so it would be an expensive experiment and there is always the question if its the correct part.
i will probably try and make my own gauge somehow and see if that gets accepted.
What year Corvette do you have? If is is a 97-2003 there is only one gauge sensor on the left tank, if it is a 2004 then it is more complicated. you are sure it is the instrument panel and not the sending unit, I have a spare Instrument panel you can have for $150 shipped in the US. Most gauge problems on the C5 are the fuel sending unit, if it is the sending unit, I have a file I can email you for the replacement if it for the 97-2003 units.
dian, try what Gordy said, the sending unit.
i found f0506. is that anything of interest?
gordy, im logging and measuring both sensors. they are in the expected range. the values change and fuel equalizes when engine is not running. i noticed the right tank showed 0.1v higher than the left so figuring the pcm maybe didnt like that i pulled the value down from 1.6v to 1.3v through a resistor to ground. left sensor being at 1.5v. no effect on gauge, however at all. im in switzerland, a us panel will not work. thanks for the offer.
its a 99, btw.
Last edited by dian; April 30th, 2017 at 09:06 PM.
Did the problem just start happening, or was anything changed...?Originally Posted by dian
First what year is the Corvette?
If it is a 1997 to 2003 it is an easy fix: GM found it was a common problem with the fuel sending unit and came up with an improved sending unit (PN 10333749) that has an improved design for longer life and better reliability. Since the cars starts and you can drive it, either the sending unit is bad or the gauge does not work. To date I have not heard of the gauge not working and all the problems lead to the sending unit. To Install the new sensor you would:
Rremove the driver-side rear wheel, the first step is removing this shield from in front of the sending unit. Next, the shield/plate that holds the tank in place is loosened, but not fully removed, so it can be pulled out of the way when removing the fuel pump/sending unit assembly. The fuel pump assembly is held in by four bolts. Before removing these bolts, disconnect the fuel lines and unplug the electrical connection. With the bolts removed, the assembly is pulled part of the way out of the tank.
Replacing the sending unit requires you to remove the wires from this plug to wire in the new sending unit. Don’t worry though, the wires are color-coded and it’s easy to push the leads out. When removing the pump assembly, it’s usually easier if you detach the sending unit part, freeing up the float arm from the assembly so it’s easier to get the whole thing out. Unplug the sending unit wires from the pump. While this job can be done without removing the whole fuel pump assembly, it’s usually easier to pull the whole thing out. The fuel sock locks in place on the end of the fuel pump and is removed by gently unlatching it from the pump and pulling it off. Before you put the new sock on, make sure you install a new O-ring on the end of the pump (usually included with the new sock or the new pump) or else you’ll end up with fuel pickup issues.
After that, the new fuel sock clips into place on the end of the fuel pump. The wires from the new sending unit insert into the assembly plug like this. The blue wire goes above the red wire and the gray wire above the black. If you get these backwards the gauge won’t read properly. With the wiring installed, the fuel pump assembly is inserted into the tank, with the new sending unit still loose from the assembly. Doing it this way ensures you won’t bend the sending unit float arm or get it tangled up with the fuel pump assembly workings. One other thing to make sure of here is your fuel pump assembly gasket is in good enough shape to be reused, or you’ll need to install a new one. Otherwise, a massive fuel leak will ensue. Next, install the sending unit into the tank, then clip it onto the fuel pump assembly. After that, check to make sure the float arm travels freely and in its full range of motion. Next, install the sending unit into the tank, then clip it onto the fuel pump assembly. After that, check to make sure the float arm travels freely and in its full range of motion. Lastly tighten the shield/plate that holds the fuel tank, install the shield and install the LR tire. HTH
so in the meantime i got the car inspected. i had it done out of state (because here they are extremely strickt) and i consider myself very lucky it passed with the fuel gauge not working and the gauges light on. last week i was also able to solve the whole problem that has been haunting me for two years.
i was on the right track with f0506 above. well, kind of. it tunrnes out f0507 and f0509 were zeroed out i the base tune i got. as f0501 is set to zero as well, i assumed the stuff was not used. i was wrong. once i found out 07/09 were populated in the original tune and copied the values over the system started working. no idea why it took me so long to find out. what made the diagnosis complicated are the two little devils f0511/12. they are set to 125 km. so after loading the base tune (that i got on a complimentary basis and that saved me a lot of trouble) i spent several weeks tuning and didnt drive the car much. when the gauge stopped working much later i didnt associate it with the new tune in any way. i rather thought it might be related to the new fuel pump i installed shortly before. well, its fixed now.
there still is something i dont understand, thought. its the third wire on the sending unit. it seems the signal comes through a 245 ohm resistor out of the ecu and gets pulled to ground by the variable resistor in the sending unit. all shematics (i have three different ones) show a third resistor being there, parallel to the variable one and i suspect thats somehow related to the third wire but i cant grasp how that could work. it my understandung there is no way, unless that third resistor is 1 megaohm or something, but then it would have no effect on nothing. if anybody has some insight into this, please share.
Posting Permissions
Reply With Quote