Olivia_2015: Doubt you'll have any problems, enjoy the Jeep and don't worry!
But, if you live a ways from a dealer or are really nervous, I would be to ask them if they looked under the vehicle and made sure there were no signs of leaks, especially with the DEF system **after** they did their test drive.
Our problem didn't cause an engine code until the wife was on the highway... even though it had been leaking all along. Apparently that's "normal" (not the leaking, but not setting the code!) To quote from the DTC for "P20EE-00–SCR NOX CATALYST EFFICIENCY BELOW THRESHOLD BANK 1" (our stored error)
The PCM requires specific engine and after-treatment conditions to be met to run and complete this monitor. There are several other criteria for monitoring this DTC including: ambient temperature exceeding -7.0°C (19.4°F), NOx Sensors are active, altitude is lower than 6,800 feet, and the vehicle has been driven at steady highway speeds for a sufficient amount of time. NOx sensor data is gathered over varying engine speeds and loads. When enough data has been gathered, the diagnostic will run, make a pass/fail decision, and begin to gather data again.
That "... the vehicle has been driven at steady highway speeds for a sufficient amount of time" is what got us. Idling in the service bay or stop/go traffic or other non-highway traffic won't necessarily cause the system to check.
The P20EE code seems to be the generic "catch all" for the DEF system not working when the computer can't identify a particular fault. The diagnostic protocol for the error is:
- Bad DEF
- Check injector for amount of DEF it sprays in a fixed test cycle
- Check for restricted hose (someone mentioned a kink hose in one of the recent threads)
- Check amount of fluid the DEF pump can pump in a fixed test cycle with the injector removed
- Run a "healing cycle" (desoot etc.)
So it's the "catch all" when it can't figure out what's not right, but it knows something is not right. Given the code isn't set until sustained highway speeds, I would just make sure the DEF line isn't leaking anywhere.
Personally, even if I bought a new one tomorrow, I would just drive it off the lot and not worry about it... Friday/Saturday ordeal didn't change my mind. I'm an optimist