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08 STS-4 N* 1SG, 08 DTS Luxury II, 04 Bonneville GXP N*
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Many GM gas gauges are notorious for this, especially if the owner(s) have used lesser grade fuels. The windings on the sensor will often corrode and as a result, there will be no contact with the wiper. Not sure about the STS but often this requires replacing the entire fuel pump as they are part of a single assembly. There are some additives (available from GM) that will sometimes correct this but they are usually a limited time cure.

There are of course other possibilities for this problem as well.
 

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2006 STS 1SG & 2007 STS 1SE
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14 Posts
The system is designed to provide a stable reading. When it's near empty, fill it up and see if it works properly.

If so, just don't get freaked-out when a small purchase doesn't register right away. It will in a while.
 

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08 STS-4 N* 1SG, 08 DTS Luxury II, 04 Bonneville GXP N*
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3,215 Posts
The system is designed to provide a stable reading. When it's near empty, fill it up and see if it works properly.

If so, just don't get freaked-out when a small purchase doesn't register right away. It will in a while.
This should not be the case if you turn off the vehicle during the fill. This doesn't apply once the ignition is cycled. The PCM will perform a new assessment on every ignition cycle.
 

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08 STS-4 N* 1SG, 08 DTS Luxury II, 04 Bonneville GXP N*
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3,215 Posts
Is it safe to assume the gas gauge sweeps the same as the others on the cluster when you first start your car?
 

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08 STS-4 N* 1SG, 08 DTS Luxury II, 04 Bonneville GXP N*
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3,215 Posts
The problem then will be either with the sender (most likely) or one of the following:

Wiring/connector from the fuel tank to the PCM.
The PCM itself (least likely).

The fuel level is sent as a serial data message from the PCM to the cluster. If there was a data bus problem to your cluster, you would notice virtually every other gauge/function would not work either.

$20.00 is a fair amount of fuel. Here, that will buy me about 1/3 tank (of premium) so there should be no problem generating gauge deflection under normal circumstances.
 

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05 STS
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512 Posts
AW as stated a GM problem. Corvettes are notorious for this. On the Corvette forum folks get pretty good results pouring a product called Textron into the gasoline. I'd look over at corvetteforum.com under the C5 technical area for more details.

On my C5 I only had the problem a couple of times and switching to a high tier gasoline cured it. High tier is hard to come by in my area so whenever I get out to an area with better gas I always stop to get some.
 

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Premium Member
2006 STS V8 AWD, '95 Ford Ranger
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29,221 Posts
The additive is called Techron and the gasoline is "Top Tier".
 
G

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Trechron will sometimes work to free up a sticking sending unit. You can buy it at any auto parts store. Worked on my wifes oldsmobile. Worth a try.
 
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