Low DEF Quality warning on 2017 4CX-14 Super

[n_frbrn]

I have a 2017 4CX-14 Super, just crossed 3,000 hours. The machine has been a tank until last week. I topped off the DEF tank last Thursday with fluid from a sealed jug, same brand I always use. Everything was until Saturday when the yellow triangle DEF warning light came on, followed by the main engine check light, and now it's stuck in a major power derate. I’m getting maybe 50% power, making loading a joke. The DEF gauge on the dash is reading fine, it's just under full. I'm getting a constant Low DEF Quality message, but the fluid is new. I’ve checked the wiring harness to the DEF pump and tank sender unit for obvious signs of damage, but everything looks okay. Has anyone experienced this "ghost" low quality warning, especially when the tank is full? Is this a bad DEF sensor in the tank, or is the DEF injector itself clogged? Trying to figure out if I can swap a sensor myself or if I need to get the dealer to plug in their diagnostic tool to reset the SCR system. Thanks for any insight!

 

[golddigg3r]

It could be a crystallized DEF injector or a malfunctioning NOx sensor upstream, both of these can set off false low-quality codes. After you make the repair, you’ll probably need a dealer reset, even if you handle the swap yourself.

 

[lifted&gifted]

Also worth checking DEF tank temp sensor if it’s reading off, it can trigger false quality faults even with fresh fluid.