Volvo - DEF gauge stuck on full

probably need new sending unit in tank need to drop out tank and replace unit make sure you drain coolant

 

Fill it up every 1000 or so miles.
I wouldn't worry about the gauge as long as I can recall when I refilled last. I'd write it down if I had to.... Speaking of, my fuel gauge has been wonky lately (reading E for 3/400 miles then clearing the fault by itself) - but everytime I fuel I reset the trip odometer to 0. Basically I know where it is & I know it's a liar.

My question of concern: Would a bad DEF gauge cause you to fail a DOT inspection?

 

No it's not a Guage that matters to dot

 

There was nothing sarcastic in my prior post in this thread. Now if you're referring to other threads around here then sure, there's some thickly laid sarcasm out there.

You must really be concerned about that DEF sensor to make your words bigger, blacker and more menacing!

I offered up a fair & legal, evidently, solution. And you want to come back all yelly about something that wasn't even part of the post. Who's problem is that, Jerry? Eh? Enlighten me.

 

In my case (Volvo 780), when I would hit a bump, the DEF gauge would go to empty and alarm would go off threatening to derate me in X amount of minutes. Then the needle would jump back to full and alarm and engine light goes away. This was going on for several days. I found that the thin red wire connected to the battery has a 30A fuse for the DEF system connected to it. I pulled off the cover to the fuse to inspect and found it was burnt, literally. I have no idea how that would have happened, but I thank God it was just a fuse. I changed it out put the little cover back on it and all issues went away. Check engine light went out after about 20 min of driving.