I have a John Deere 333G skidsteer with code DCU 3516.01 that is active and it also says "outlet nox sensor very high" which is stored but not active. We were told it was the DEF metering setup, but the part is 3k and dont want to just purchase one if this is not the problem. Serial # is 1T0333GMKJF335769 and the year is 2018. Appreciate any insight to the issue.
Welcome to HEF js ! That code is a DEF quality code. First step is to check the def quality with a refractometer. If it is no good, then a tank draining, cleaning and refill is in order. If the refractometer says it is good, then the reading needs to be checked with someone with Service Advisor to see what the ECU sees. It is possible the DEF header may need replacement. Also, your machine has new software available for the DCU which does change the thresholds for what sets that code. So I recommend getting the software updated as well.