T-stat issue on 00 Tundra?

[JScott]

I've got a persistent check engine light that started Friday morning up at LOW (-20).

Temp. gauge says she is running cooler than normal (exactly half way between the marks even during prolonged travel) and we noticed the heater/defroster just wasn't kicking out like usual.

Should I be suspecting the T-stat? It looks easy to get at, anything tough about getting it changed out? Coolant is two years old, T-stat is original.

[Jeremy airjer W]

sounds like a good start to me. If I remember right the code is P0125 - insufficient coolant temp for closed loop operation. Even with temps that low you should be able to get quite a bit of heat of the vents.

[BIG DS]

I guess that I would take it somewhere to find out what codes were popping up causing the check engine light to come on. You probably have a thermostat that is stuck open a bit. But, keep in mind, with air that cold, your engine takes a very long time to heat up and the heater has to work very hard just to take the chill out of the air. Remember, if your asking for 70 degree air in the cab, at -20 you are trying to raise the temp 90 degrees. A lot to ask of any heater. Some sort of winter front to cover the grill makes a big difference. A lot of people put cardboard behind the grill to help on cold days like that. Do not put it directly on the radiator though as that will cause it to overheat. Check around with some of the parts stores, there are some grill inserts that you can get that look real nice and help a lot on cold days like that. I had them for my Dodge Ram and left them in the grill all winter. They work good.

[JScott]

I decided to bring it in, and they found a bad O2 sensor. Not surprised I guess. Made 8 years without any issues of any sort with the truck so I can't ask for more than that. I may have been wrong about the T-stat being bad. It was awfully cold up there.