Wouldn't I get a CEL if I throw a code?

I replaced the FCA two weeks ago but the thing came back yesterday. The truck started to idle up and then all of a sudden a surge happened. Turned her off and did the key swithc code check it read p0251. Had here cleared at the local auto store and drove a few miles back home. Wouldn't the code come back if it was bad?

Thanks,
Dwight

 

Bump....

 

My truck threw the code twice it has only happened this winter. i talked with a cummins mechanic and he said that its because its cold ive never had an issue other than when it was real cold. i added a plug for the block heater and started using it an time its in the 30s or less and have not had issues since. the mechanic also told me if i got the high idle ingaged and used it every time i started it in cold weather that it would prevint it to. hope this helps.

 

Well, I just threw the code again. If I didn't know the key code trick I would have never known it did it. Truck runs fine, no smoke, no wierd idle, has power. Gonna take a look at the wires to see if they are bad or the connectors are getting a good connection.

Now my question is if throwing this code is bad why no CEL? I am under the impression that a bad FCA can ruin a lot of things. How would a normal person who isn't **** about checking things like this supposed to know if something is wrong???[\

Please help