"engine control fault" and a theory.

[eddycelis]

I live in Florida and two to three times a year I go to North Carolina for a driving vacation. I trailer the car there and back.
Been doing this with my 2019 BGTS and now since last year with my 2023 Spyder.
First time with the Spyder was in October. Loaded up, strapped the car to the trailer. No problem.
When I arrived in NC, I start the car on the trailer to back it off the trailer and within a minute I get the "engine control fault" popup. The popup said "driving permitted" so that is what I did. The popup disappeared while driving and did not come back until weeks later when I was back home. I had the code cleared by the dealer and they said that it was for low fuel pressure and that they cleared the code and checked the fuel pressure and that everything was OK.
End October I decide to head back to NC. Sure enough the same error popped off while backing it off the trailer in NC. Again it disappeared while driving and when I checked and reset it with my own scanner after coming back home, it again said it was for "Fuel pressure regulator performance".
And now last June I head back to NC for the Rennsport Dragon Rally and you can already guess what popped up when backing it off the trailer in NC.
So that is three times trailering, three times a problem. !00% is no coincidence.

So my theory is that the car software gets confused when starting the engine after the sudden (for the car) 2000 feet of altitude change between Florida and NC ?!?

[Tom]

Interesting. Can't say I've ever heard of that, but you could certainly imagine several ways for that to happen. If others can replicate it, it feels like the kind of thing that could be coded out with a software update. You could imagine the ECU throwing a code if you shut the engine off with X amount of pressure and turn it back on with quite a bit less. I wonder what would happen if, next time, you run the motor at several interim elevation points along the way up?

I kind of wonder about your pressure sensor though. You'd 'think' if this is just a glitch that affects all Spyders, you'd hear other people talking about the same issue -- although maybe the universe of people towing their Spyder to a higher elevation is too limited for that.... Would be pretty telling if you towed another Spyder and it didn't do this.

[SirLapsalot]

Do you recall the specific P-code that was set each time? Was there any on-board snap shot data your generic code reader can display? I wouldn't be surprised if it was an actual physical phenomenon that's triggering the failure code rather than a software bug.

IDK how high up in the mountains you're going in NC but in the past we had lower RVP fuels in high altitude vs. normal altitude. If your car is being trailered up to NC with Florida fuel in the fuel system, then I suppose it wouldn't be super surprising if you experienced some level of vapor lock when you start it up in altitude. Not familiar with 2019BGTS vs. 2023 Spider but if they have different DI system operating pressures then that could be the reason one sets a MIL and the other doesn't.

[eddycelis]

Interesting. Can't say I've ever heard of that, but you could certainly imagine several ways for that to happen. If others can replicate it, it feels like the kind of thing that could be coded out with a software update. You could imagine the ECU throwing a code if you shut the engine off with X amount of pressure and turn it back on with quite a bit less. I wonder what would happen if, next time, you run the motor at several interim elevation points along the way up?

I kind of wonder about your pressure sensor though. You'd 'think' if this is just a glitch that affects all Spyders, you'd hear other people talking about the same issue -- although maybe the universe of people towing their Spyder to a higher elevation is too limited for that.... Would be pretty telling if you towed another Spyder and it didn't do this.

You are right that more people should run into this problem, it is not only Spyders, but GT4 and GTS4.0 as well.
(Part of the reason I'm posting this is to lure those out...)

[eddycelis]

Do you recall the specific P-code that was set each time? Was there any on-board snap shot data your generic code reader can display? I wouldn't be surprised if it was an actual physical phenomenon that's triggering the failure code rather than a software bug.

IDK how high up in the mountains you're going in NC but in the past we had lower RVP fuels in high altitude vs. normal altitude. If your car is being trailered up to NC with Florida fuel in the fuel system, then I suppose it wouldn't be super surprising if you experienced some level of vapor lock when you start it up in altitude. Not familiar with 2019BGTS vs. 2023 Spider but if they have different DI system operating pressures then that could be the reason one sets a MIL and the other doesn't.

We are going from 12ft above sea level to 2100. Maybe hitting higher on the way there.
The car starts like always, no hesitation or shudder, nothing abnormal. A vapor lock would cause it to hesitate starting, right?
2019 BGTS is the 4-cyl turbo, so completely different engine.
The two last times it was the same P-code. Do not know the first one as the dealer checked it. I do not think my cheap reader can snap shot the actual data.

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[J-Dub]

I really want to contribute to this thread but just don't have any theory on this right now.

Maybe, on the next trip as a test start the car while it is on the trailer several times when the tow vehicle is stopping for gas so that the delta in altitude, barometric pressure, between starts is reduced.

Would you say this is check engine light is more likely to happen on a start where you are significantly higher in elevation than the previous start?