08 C6 fuel level sensor voltages
03-07-2016, 10:41 PM
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08 C6 fuel level sensor voltages
I just replaced the left sending unit, because it cracked as usual.
After replacing it and filling it up it gave me the lovely "service fuel system" warning and went to empty.
I used a scan tool to measure voltages on the sending units. When full I get the following.
Left tank reads 2.54V
Right tank reads 0.71V
I jumped the pump and drained it until It was empty, which is just the left tank emptying. The voltage dropped to 0.71V on the left and stayed 0.71V on the right.
One I hooked the fuel line back up svc started the car the right tank, as I believe it should, started transferring to the left. On the scan tool I can see the right voltage dropping and the left rising.
I don't have access to the service manual to diagnose it better, but I did find this for a C5 and would like someone to confirm is the same for the C6.
https://www.google.com/url?sa=t&sour...WDlP_oYljWakog
As I didn't change the right sender, I believe it is functioning properly, low voltage when full, high when low.
Old left sending unit is high resistance empty and low resistance full.
I suspect that the new unit has the wrong level sending unit, but without the service manual, I can't be sure and would like to verify prior to dropping the tank(s) again, because that's no fun.
Thank you in advance.
After replacing it and filling it up it gave me the lovely "service fuel system" warning and went to empty.
I used a scan tool to measure voltages on the sending units. When full I get the following.
Left tank reads 2.54V
Right tank reads 0.71V
I jumped the pump and drained it until It was empty, which is just the left tank emptying. The voltage dropped to 0.71V on the left and stayed 0.71V on the right.
One I hooked the fuel line back up svc started the car the right tank, as I believe it should, started transferring to the left. On the scan tool I can see the right voltage dropping and the left rising.
I don't have access to the service manual to diagnose it better, but I did find this for a C5 and would like someone to confirm is the same for the C6.
https://www.google.com/url?sa=t&sour...WDlP_oYljWakog
As I didn't change the right sender, I believe it is functioning properly, low voltage when full, high when low.
Old left sending unit is high resistance empty and low resistance full.
I suspect that the new unit has the wrong level sending unit, but without the service manual, I can't be sure and would like to verify prior to dropping the tank(s) again, because that's no fun.
Thank you in advance.
03-08-2016, 12:31 PM
#2
Le Mans Master
See here for more:
https://www.corvetteforum.com/forums...post1590738015
03-08-2016, 03:27 PM
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The good news is that you can apparently reverse the sender calibration with a tune, allowing a later model C6 to use early level senders and vice-versa, or a mix of both.
See here for more:
https://www.corvetteforum.com/forums...post1590738015
See here for more:
https://www.corvetteforum.com/forums...post1590738015
I'm not interested in spending money on a tune when Delphi put the wrong sensor on it.
Looks like I get to drop the tank AGAIN, because it was so much fun the first time.
I would still like to see a FSM to verify voltages and resistance on the 08.
Tim
03-11-2016, 01:46 PM
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Thought i would update for future tech help, assuming people search for it.
Because of this issue I get P0461.
I talked to Delphi and they have the same part number for all year C6's and insist that they are not different. Even though multiple times I proved them wrong, they wouldn't relent from the story that they make them exactly like GM does, and it works fine.
The Delphi part number is FG1091 so don't buy it ever, unless you are going to, or already have a tune in the car.
I ordered the proper one from GM but they were on back order and i needed the car so i bought the Delphi one.
So what I'm going to do is drop the tank again and switch the potentiometer for the float from my old unit.
I tried to get somewhere with a labor claim for delphi, but they know everything, just ask them.
Tim
PS, screw Delphi.
Because of this issue I get P0461.
I talked to Delphi and they have the same part number for all year C6's and insist that they are not different. Even though multiple times I proved them wrong, they wouldn't relent from the story that they make them exactly like GM does, and it works fine.
The Delphi part number is FG1091 so don't buy it ever, unless you are going to, or already have a tune in the car.
I ordered the proper one from GM but they were on back order and i needed the car so i bought the Delphi one.
So what I'm going to do is drop the tank again and switch the potentiometer for the float from my old unit.
I tried to get somewhere with a labor claim for delphi, but they know everything, just ask them.
Tim
PS, screw Delphi.
03-11-2016, 07:21 PM
#5
Le Mans Master
https://www.delphiautoparts.com/en/t...-level-sensor/
To wit, Delphi states specifically:
The 2006 version of some models has a float level sensor in which the fuel level increases when resistance increases. In 2007, General Motors changed the architecture of the cluster on some vehicles, making the gauge now work ‘backwards.’ Thus, if a fuel level sensor for a 2006 application is installed on a 2007 application, the gauge will read opposite – when the tank is full the gauge shows empty, and when the tank is empty the gauge shows full. The key to prevent this is to check your application. Make sure you are using the correct part for the correct year application.
03-11-2016, 07:45 PM
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Show them this, their own GD web page:
https://www.delphiautoparts.com/en/t...-level-sensor/
To wit, Delphi states specifically:
https://www.delphiautoparts.com/en/t...-level-sensor/
To wit, Delphi states specifically:
Wow, thank you for this.
I'll have to give them a call again on Monday. What a PITA.
03-12-2016, 12:03 AM
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St. Jude Donor '15
Where are you located?
03-12-2016, 12:35 AM
#9
Le Mans Master
This is a GM technical note from nearly 10 years ago:
Fuel Level Sending Units Revisited
Operation of a typical in-tank fuel level sending unit is based on variable resistance. As the float moves up or down according to fuel level, the resistance in the sending unit varies. This varying resistance is processed by the engine control module (ECM) and the resulting information is sent to the instrument panel cluster (IPC) for display on the fuel gauge.
In the past, the sending unit was set up so that high resistance indicated high fuel level, and low resistance indicated low fuel level.
Sulfur contaminants found in some of today’s gasolines can form deposits on the sending unit (fig. 12), resulting in higher-than-intended resistance (TechLink, Jan. 2006). The high resistance from the deposits could be misinterpreted as a high fuel level, when in fact the fuel level is low. The driver may run out of fuel, even though the fuel gauge is not indicating low or empty.
To offset this effect, engineering has begun “flipping” fuel senders, reversing the circuitry. This means that high resistance now indicates low fuel level and low resistance indicates high fuel level. So, if deposit build-up adds to sender resistance, the gauge will err in the direction of indicating less fuel than is actually in the tank.
The “flipping” process began in the 2004 model year and continued through model years 2005-06.
These vehicles will have their fuel level sending units “flipped” for the 2007 model year.
- Cadillac XLR
- Chevrolet Corvette
- Chevrolet Impala, Monte Carlo
- Chevrolet Malibu
- Pontiac Grand Prix
- Buick LaCrosse (Allure)
These vehicles will have their fuel level sending units “flipped” for the 2008 model year.
- Cadillac CTS
- Cadillac SRX
- Cadillac STS
TIP: When diagnosing fuel sender operation, it’s critical to refer to the appropriate model year information in SI, to be sure which resistance specifications apply.
TIP: GMSPO offers GM Fuel System Treatment PLUS p/n 88861011 (88861012 in Canada) which helps protect fuel sending units from contaminating deposits.
Operation of a typical in-tank fuel level sending unit is based on variable resistance. As the float moves up or down according to fuel level, the resistance in the sending unit varies. This varying resistance is processed by the engine control module (ECM) and the resulting information is sent to the instrument panel cluster (IPC) for display on the fuel gauge.
In the past, the sending unit was set up so that high resistance indicated high fuel level, and low resistance indicated low fuel level.
Sulfur contaminants found in some of today’s gasolines can form deposits on the sending unit (fig. 12), resulting in higher-than-intended resistance (TechLink, Jan. 2006). The high resistance from the deposits could be misinterpreted as a high fuel level, when in fact the fuel level is low. The driver may run out of fuel, even though the fuel gauge is not indicating low or empty.
To offset this effect, engineering has begun “flipping” fuel senders, reversing the circuitry. This means that high resistance now indicates low fuel level and low resistance indicates high fuel level. So, if deposit build-up adds to sender resistance, the gauge will err in the direction of indicating less fuel than is actually in the tank.
The “flipping” process began in the 2004 model year and continued through model years 2005-06.
These vehicles will have their fuel level sending units “flipped” for the 2007 model year.
- Cadillac XLR
- Chevrolet Corvette
- Chevrolet Impala, Monte Carlo
- Chevrolet Malibu
- Pontiac Grand Prix
- Buick LaCrosse (Allure)
These vehicles will have their fuel level sending units “flipped” for the 2008 model year.
- Cadillac CTS
- Cadillac SRX
- Cadillac STS
TIP: When diagnosing fuel sender operation, it’s critical to refer to the appropriate model year information in SI, to be sure which resistance specifications apply.
TIP: GMSPO offers GM Fuel System Treatment PLUS p/n 88861011 (88861012 in Canada) which helps protect fuel sending units from contaminating deposits.
And was also mentioned here on the Forum: https://www.corvetteforum.com/forums...post1557760810
03-12-2016, 08:37 AM
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St. Jude Donor '15
03-12-2016, 09:33 AM
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I appreciate it, but I already have a tuner local. I also already have EFI Live so it wouldn't be any trouble to do it, except that I shouldn't freaking have to spend money on credits to fix a Delphi screw up.
03-12-2016, 01:06 PM
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St. Jude Donor '15
You shouldn't have to, sure.. but at some point it's easier to just change the the tune and be done with it vs. pulling the tank back out/apart, etc.