Her yellow light has been on for at least 5 days. The following is an interesting read but just because its on the internet, I ain't beleiving it.
"I've been reading up on the DeRate aspect of a DEF Header failure. It appears that some OEMs have reached an agreement with the EPA to allow an Emergency Authorization Override that allows the DeRated vehicle to operate without the DEF system for a period of time. There is some reporting requirements but that sure beats sitting on the side of some roadway in "who knows wheresville".Also, Cummings/Freightliner appears to have either a reset or override triggered by a series of key turns and power resets that may help some get to a Service Center without a tow.Happened across this on the other forum:"Anyway... that night, I put the key to the left for two hours as suggested by Freightliner who said that sometimes clears the codes. In the morning, per a youtube video, I shut off the chassis batteries for 15 minutes. I also unplugged and turned off the house batteries for good measure. After 15 minutes, I turned the key to the right halfway not starting the engine. I let the system power up for 15 seconds or so and turned the key back off. I repeated that procedure 4 times and then started the engine. I still had the red stop engine light on and I assume I was still d-rated. I let the engine run a while... I'll guess at least 5 minutes. It sure seemed like a long time. After a couple of minutes, the flashing red low def level light went off and the gauge read correctly at 3 green bars. After several more minutes, the Red stop engine light went off and the system was normal. Excited to avoid a tow or a mobile tech, I started the 41-mile drive to Velocity in Tucson. After 10 miles, the orange service engine light came on and the DEF level flashed red, and it remained so the rest of the way. ....."