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Discussion Starter #1 (Edited)
Hey guys,

So I drove my 2006 9-5 into a car wash with the gas cap hanging off. Didn't realize it until the dryers turned on and I heard the cap knocking around in the wind. I know, stupid. Anyway, the next day I got a code P1455 - EVAP Tank pressure sensor - Serious leakage in system and malfunctional fuel level sender.

It's strange the code didn't come up until the next day. So I am not sure if the code is related to the gas cap off incident, or something else.

I do have a wonky fuel sender issue where my gauge reads empty after a fill-up until about 30 miles, and then it seemingly comes back to life. But I've had that issue forever and it has never set a DTC code before.

I cleared it with Tech 2...I'll see if it comes back and post here when I figure it out. Starting a thread in case anyone else has this issue. Car seems to drive fine. I don't hear about this one too often on the forums.
 

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The Fuel level sender is unrelated. The onboard computer will test the pressure in the fuel evaporate system and since the cap was off, it did not pressurize, thus setting off the trouble code. The light would have gone out after several drive cycles. It should not come back.
 

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Discussion Starter #3
The Fuel level sender is unrelated. The onboard computer will test the pressure in the fuel evaporate system and since the cap was off, it did not pressurize, thus setting off the trouble code. The light would have gone out after several drive cycles. It should not come back.
I would have agreed with you wholly, but I looked up the P1455 fault codes in WIS. It's a fun (not) read, but the part that caught my eye was this:

Fuel level, reasonability diagnosis:
Because fuel level is used as an enable criterion in certain diagnoses, the control module must know that the fuel level value is reasonable. This occurs in the following manner; Trionic receives the bus message ”Fuel level XX litres" from the MIU. Trionic monitors the value and knows that the fuel level value should sink while the car is being driven. There are several value filters in Trionic which help to avoid discrepancies such as sloshing in the tank or starting on a hill. The fuel level diagnosis can be seen as a support diagnosis; it reports no diagnostic trouble code but P0455 is normally set if the tank seal diagnosis reports a large leak for example. If, however, the tank seal diagnosis has reported the same fault at the same time as the fuel level diagnosis has reported a fault, P1455 is set instead.
It makes sense, because my fuel level was showing 0 (while being actually full) when the gas cap was off, so it set P1455. I think P0455 is the code that is normally set. But as I mentioned I've had that problem with my fuel sender for a long time, and have chosen to ignore it until it dies completely. Anyway I cleared the code and it hasn't come back, so I'll chalk this one up to me being an idiot. 🤪
 

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Intriguingly, I drove my 2004 9-5 320 miles in February with the gas cap in the holder on the metal cover, which of course had blown back in the slipstream and held the cap safe against the car.

No DTC/CEL and no Fcod in openSID.
 
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