Chrysler Repair: 03 Chrysler Voyager 3.3 Cooling Fans

Question
Changed the radiator in a 03 Voyager with 3.3L and the check engine light came on afterwards.

Here is step by step what has been done.

1. Changed radiator. Without disconnecting battery.
2. Refilled coolant, heater on while topping off.
3. Fans and heat worked during topping off.
4. Noticed check engine light on.
5. Removed negative cable from battery and replaced. Both fans started running immediately, engine cool, keys in pocket.
6. Removed positive cable from battery and replaced. Both fans shut off, and will not run with engine running and temp coming up.

Just wondering if I triggered the engine code by not disconnecting the battery before starting and disconnecting both fans.
Pretty sure all relays and fuses were working fine until I disconnected the battery.
If I clear the code with a scanner will it reset everything back to normal?  What am I missing?

Answer
Hi David,
The radiator fans are powered by fuse 27, 40 amp via the fan relay which is controlled by the pcm which is looking at the coolant temp sensor to decide when to power the fans. Check the fan relay also which is located behind the grille on the top of the chassis side rail near the left headlamp.
Do you have a code reader? If not, turn the key: "on-off-on-off-on and leave on" doing that in 5 seconds or less elapsed time. Then watch the odometer window to see the mileage erased and be replaced by a 4-digit number preceded by a P. Let me know the number and we'll go from there.
I am not sure why the code set, but knowing the code number will shed some light. By merely disconnecting the - post of the battery and then reconnecting it you will erase the code (except for a code that says "battery disconnected recently" which will go away on its own accord after 50 or so starts).
About the fans not operating, it may be that you have air trapped in the system, and if some of it is in the thermostat housing then you will get a false cool reading of the coolant temperature until the air is expelled. Thus the fans may not get a 'cue' to operate from the powertrain control module. That should happen quickly, so watch for signs of overheating until the fan control (coolant temp sensor) starts to read accurately. Check coolant level in the overflow bottle as it will drop down as air is expelled.
Please read the PS (below) and respond to it.
Thanks,
Roland