New to this forum, to Jaguar and Diesels, please be nice. I've been researching this issue for several weeks now and still haven't been able to find a solution.

Backstory:
About two months ago I got the dreaded DEF quality message...No start after XXXKM. I naturally panicked a little and topped up DEF fluid and went for a drive hoping it would clear, it didn't. Did more reading and was guided to check DEF injector for crystallization, there was some there so I cleaned it up and went for another drive, still no luck. Then someone mentioned I should clear the DTC to get the dosing message, which I did but after another drive it persisted. I then took it to a Euro Car mechanic near me that has Pathfinder diagnosing tools and he narrowed it down to NOx sensor. CAD$1200 later and two days the DEF message comes back. I decide to replace the injector, clear DTC and after about 3KM drive message clears but CEL stays on P249D. Did some googling and it seems pretty vague. Next day DEF message comes back again so I decide to take it to a Jaguar dealer, they run their diagnostics for a small fortune and determine there were issues with the fluid itself and an overfill error. They did a flush cleared all codes and sent me on my way. Start the car and CEL turns on so I drive it up to their service bay, they run their diagnostic again and find P249D DTC. They told me they're not sure what the code means and said I should drive around for a couple weeks and go back for another diagnostic.

Now I'm stumped, no one seems to have any ideas as to what could be causing the issue. I've been driving with this CEL for a few days now, cleared a couple times but it keeps coming back. No other codes come up (I ordered a more advanced scanner which should be able to access more modules for codes, today hopefully). Though it seems it's just a persistent DTC, if there were an issue with the DEF/AdBlue system that message would have come back by now (My trips to work are 60KM's one way mostly Hwy).

Hoping someone here has some wisdom to share, I've got no hair left to pull.

 

I assume the car is a Canadian registered car, and a diesel. There have been problems with the DEF equipment here in the UK so I suggest you have a look on this XE-specific UK forum where DEF faults have occured on cars. One thing you don't mention is the DEF injector. I believe this can get clogged-up and the downline detector finds too much Nitrogen dioxide in the exhaust gas, and flags a fault. Here in Europe, AdBlue is on sale literally everywhere ! The majority of XEs were diesel until recently.

Jaguar XE Forums - Jaguar XE forums and discussion for all UK owners.

 

Fraser, Thanks for the suggestions and link. I did replace the injector as well, below are some more details on readings from the new scanner.

There are 5 issues for Vehicle body system：
1.[P249D-00] Closed Loop Diesel Exhaust Fluid Injection Control At Limit - Flow Too Low
2.[P20EE-04] Selective Catalyst Reduction NOx Catalyst Efficiency Below Threshold - Bank 1 - System Internal Failures
3.[P20EE-92] Selective Catalyst Reduction NOx Catalyst Efficiency Below Threshold - Bank 1 - Performance Or Incorrect Operation
4.[P20EE-96] Selective Catalyst Reduction NOx Catalyst Efficiency Below Threshold - Bank 1 - Component Internal Failure
5.[P20EE-00] Selective Catalyst Reduction NOx Catalyst Efficiency Below Threshold - Bank 1 - No Sub Type Information

I found that while driving the SCR temperature readings were high, 450C - 500C under light load. I think the normal should be around 200C - 300C, not sure if the sensor is faulty or there is something else...