Engine Code - 2004 9400i with Cummins ISX

I'm getting what seems to be a "low coolant level" code: 128:F01
My coolant level was a little low but the code continues to appear 3 days after topping it off.
I've also noticed that at idle the water temp can go up to 220. Once I get on the road it will stay in the 180-183 range. I'm not sure if the water temp is normal for this truck or if it's related to the coolant level code issue.


It it seems that this started happening after the water was drained in order to replace a broken exhaust manifold bolt.

Any ideas as to what could be causing the engine code? I've thought about replacing the radiator cap and maybe what looks to be the coolant level sensor, since they are easy to get to, but I don't want just "throw parts" at it if I don't have to.
Thanks in advance for any help.

 

thanks Heavyd.
Yes, the Warn Engine light does come on and then the LCD will display the fault/code.
The fan does not come on at 207, it will turn on if I engage it manually though.

 

Thanks again Heavyd and Baha. Your input is greatly appreciated. I'll let you folks know what ends up happening.

 

Here's a quick update.
A mechanic buddy gave me some useful info. It looks like the fan will not come on until roughly 220 degrees if the AC is off. Sure enough, I turned on the AC and the fan is coming on and keeping me right at 180
he alo said that 95% of the time the low coolant codes are a result of a bad sensor. I'll see if I can get to the dealer this afternoon to pick it up and replace it. I'll let you folks know what happens. So far, I'm a happy driver!

 

I replaced the coolant level sensor this morning and ran all day without the "warn engine" light coming on! It would've come on within the first hour.
I appreciate everyone's input.