The past two weeks have had us at -25 here in Anchorage. My truck has been throwing a check engine light on cold starts. After the truck has run a bit and warmed up the light normally goes out. I haven't been by the Dodge dealer yet to see what code it is throwing. Anyone else in the cold climates have this issue. This is a first as it normally isn't this cold here in Anchorage.

 

Turn your key on/off 3 times without starting, then leave in on position after third time. A pxxxx code should show up in the odometer, may be more than one. Take a pen with you, right them down, then, post what you have found. Have to bet on fuel or battery issue at those temps.

 

Had a similar problem last winter. Can't remember the code but had to do with temp conflicts. -20 for extended periods here mainly set code off when truck was plugged in. Finally bought a code reader that would clear codes after 3 trips to dealership.

 

Well I ran the truck a little longer today with a trip to the far side of town. I guess the extra heat in the engine did something because it cleared out the CEL. It just seems that anytime I have a cold weather start I get that darn light until things warm up. About time to get a clearing machine/tuner. I will need that for the rest of the mods coming when it is warm enough to work on the truck. The -20 deg and fingers doesn't work so well for doing dpf delete and egr delete. By the way my mileage is really bad right now because of the fuel getting dumped in the exhaust to try and raise the temps for regen. It has gone down to 11.5 mpg with the really cold weather. Yet another reason to do some work in warmer times.

 

I'm willing to bet that the code you're getting is P0128 - Thermostat Rationality. There are a ton of sensors on these rigs. From what I've experienced and witnessed, this code only shows itself during the winter months. Make sure you've got the latest flash update (AZ for the '07 6.7L). I had the same problem last year... code would come up and last for roughly a week, then the CEL would go out. I believe that what they did with the later flashes was to increase the tolerances allowed by the ECM between the coolant temperature and those of the other sensors. Basically, when there is too big of a difference between them, it throws a CEL. Let us know what you find.