Got the damn "check engine" light after changing my gas cap (old cap appeared to be venting, made the side of the truck look like it had mold or mildew on it). Here are the code numbers and explanations:

PO442
Definition
EVAP (evaporative emission system) small leak/ no flow condition
Explanation
The evaporative emission system is monitored for it's ability to hold vacuum.
Probable cause
1- Defective or loose fuel cap
2- EVAP canister or hose cracked-not connected
3- Purge or vent solenoid defective
4- Vacuum leak at engine


PO455
Definition
EVAP large leak detected
Explanation
The ECM has detected a large leak in the EVAP system during a system monitor test
Probable cause
1- Defective, loose or missing fuel cap
2- Evap canister broke, hose cracked or not connected
3- Purge or vent solenoid defective
4- Vacuum leak at engine


As I stated, I changed the fuel cap and the problem(s) started. I did a quick check of the exposed hoses to see if anything was obviously cracked or not connected- didn't see anything wrong. Is there a field method to check the solenoid for function? The reason I'm asking these questions is to see if anyone else had this problem and what their solution was. I have had my truck in the shop a couple of times for different problems (which turned out to be relatively simple, albeit expensive, fixes) and after knowing what the fix was, I was able to save my son (he has a '03 Ram 1500/4.7 L) a lot of money by pointing to the problem and letting him repair it himself. All troubleshooting/repair info will be greatly appreciated!! Thanks.

 

Light is still on- btt