Very very odd thing happened. Driving up from Houston to Colorado yesterday. Snow tires mounted in preparation for the snow in NM and CO. Around 300mi into the trip, the CEL (check engine light) came on. No idea why. Because I was on cruise control, I did not notice the lack of power. Checking the battery, it was in the purple. I first opened the gas cap and screwed it back in. I figured the change in elevation or temperature may have had something to do with the CEL. Nothing. Gas tank was a quarter full. At Lubbock, I pulled over and filled up. I played with the rubber gasket on the gas cap but decided it was going to be more trouble than I was prepared to deal with, without any tools. CEL stayed on for another 30minutes or so while I navigated through the city, covering another 20 miles or so. After a pitstop to pick up OJ, I started the car and the CEL was off. Very very odd. Here are the variables: Elevation delta - +3000 ft Temp delta - -10F The only thing I can think of is that the hybrid battery is getting long in the tooth (2008 MY, 103k mi), the wind in the high plains chewed through the battery power, and the long length of being in low charge got the ECU to confuse itself into thinking that the hybrid battery has bad cells. . .which it probably has a few weak cells. What's everyone else's thoughts? I'm in Albuquerque, NM now. Since Lubbock, I haven't had an issue. That's about 350mi of climbing elevation (another 1500 ft) with the battery often in purple for long periods. Temp delta of -30F.
It is at the mileage that you may notice it burning oil. Have you checked the level? Also, the CEL is known to come on with a build up of fumes in the bladder. It is possible that removing the cap let the fumes escape, thus the light turning off... Do you have movement in the inverter coolant holding tank with the car in ready?
When I've had EVAP codes in the past, they've taken some mileage to clear even after the issue is resolved. Perhaps it was a simple as a loose gas cap. You didn't mention oil level check so I'd do that right away at least for peace of mind. As you'll read here on PC, a 12v battery going bad will cause anomalous behavior. I'd get check the 12v battery first, then when you reach your destination, if you haven't already, get an OBD reader and find out what codes your car is throwing.
This may not be relevant to a Prius at all, but when we have driven Accords, Civics, a Jetta diesel through the mountains in Pennsylvania and the Virginias the check engine lights come on. Some of them reset when one stops at rest stations and some don't. Bottom line, according to the dealers we have consulted is that all of our cars' computers have decided that normal air pressures are those that exist in the Great Lakes Basin and they are confused by the lower air pressures at altitude and that it is not important. On Canadian models, by the way the CEL is a picture of an engine - scarey.
I'm guessing it was the delta in elevation. Now, I'm at 9500ft. Between Lubbock at 4000ft and now, no issues. Well, other than anemic power whilst my trying to whip her to maintain 80mph. As one might expect, my mpg was. . .35mpg. Still remarkable. Haven't checked oil. That'll be tomorrow morning. Ditto with inverter fluid. Inverter fluid was changed as part of steering wheel recall. . .when it COMPLETELY failed! Ha! I suppose that's worth another thread. . .
Oh, and I stupidly forgot to bring the radiator blockers I'd fashioned from pipe insulation. That would have been more useful fuelwise last night as I camped in the car (I always do that when I come up here).
Plenty of drivers frequently travel that elevation gain, and far more, without any 'convention wisdom' of it triggering CELs. So I'm skeptical of that one.
