Idk but every time I get def from the pump I get check engine. Going to get def from walmart and if check engine will go off and stay off I'm done with def from the pump
If you let it get too low it will put check engine light on. It will eventually derate the power. Then it will knock you back to 5 mph. Eventually it will shut down and demand you see a dealer to plug in to eco to allow it to go again. There is a def filter and it does need changed periodically. It has quite a long time between changes and yours may not have been done in a long time. You see how it crystallizes on the nozzle tip? Same thing happens inside and it eventually plugs it up. That may be your issue. Buying it by the jug is very expensive.
At Pilot... The def units and nozzles are rather filthy and caked up. Diesel is one thing because there are a dozen filters between the pump and the truck itself But def... very very sensitive stuff when it comes to malfunctions and injectors and what not