New Expy owner w/ engine codes

[Fastcat]

I just purchased a 2000 Expy from a local auction and there are 2 codes popping up. I dont have the exact code numbers on me Ill post them a little later but 1 was for engine running too cool. And the other was bank 1 running lean or misfiring. But the engine runs perfect and the tranny sifts perfect. Any help what to do 1st would be appreciated and I will post the cods a little later thanks!!

 

[tmajikman]

Let us know the codes so we can assist you better. The codes help determine the right course of action to take.

 

[Fastcat]

Ok the codes are p0125 and p1131

 

[tmajikman]

Replace the thermostat. That code sets when the engine doesn't reach operating temperature, which will cause the truck to stay in closed loop and the fuel trim tables will not adjust properly if the truck is in open loop status. If you can do some diagnosis, leave the truck idle for 5-10 minutes, if the upper rad hose is warm to hot, that would indicate the thermostat may be stuck open, it should stay cool until the thermostat opens then get really hot. Don't usually see a lot of problems with the coolant temp sensor itself but i'm sure they do fail

 

[Fastcat]

Would that cuase the lean condition on bank 1 also? I had the engine running about 20min and the upper hose is still just slightly warm not hot at all. Guess that explains why I made a 300 mile trip wit heat on full blast the whole way back and forth and i never had to adjust the heat setting!