Reduced Engine Power notice and Altitude???

[Paul and Sue]

I got this strange thing that occurr only in one location, I-8 going from Arizona to San Diego. I make this run often and this happens all but one time.

Going west on I-8, I stop for gas at the casino close to Pine Valley, California which is about 4200 feet altitude. As I go down the mountain into San Diego which is at sea level the Reduced Engine Power goes on. I pull over, sit for a few minutes, re-start and drive off OK. The first few times I took the W-22 to the shop and they say there are no codes listed. As you can tell it took many trips like this to get the info to this point. Now it does not happen going back to Arizona which is about 1500 feet altitude. I have changed the gas cap and the W-22 runs good so I don't think it is bad gas. When I go down into San Diego, I make sure to stay in the curb lane getting ready to pull over when the notice and engine shut down.

Any Ideas?

[max49]

I'd guess it's just the electronic fuel injection adapting to altitude changes and trying to keep the fuel/air mixture as close to optimal as it can. IMO, the 'Reduced Engine Power", limp mode and/or check engine light just come on because the parameters set into the computer are just too narrow for many real life scenarios. That's why I call it a false alarm. At leasting, "Rebooting" the engine brings all back to normal, except the check engine light often remains on.
Mine has done it on very long slight downhills , maybe 75 or 100 miles, from 10,000' to 5000' elevation. This is where I can honestly average 15 or 20 MPG, and I think the computer or the ECM actually has a problem accepting that.

[Full-Timers]

Try changing the air filter and clean or replace the MAF (Mass Air Flow) sensor.

[lakewoodpaul]

I had that happen to me on my 03. It happened once in the mountains of w.v and other times at near sea level. actually it happened 3 times in 80k mi. Unforchanalty the engine light never stayed on long enough for WH to see a fault on their diagnostic tool. Still a mystery, dont thimk altitude had anything to do with my problem.