Cummins isb 6.7 b101 cm2350 dozing pump issues

[joed2323]

Now I tried doing the def pump override test and it will never go into the test with key on engine off.
That def fluid pressure seems to have a mind of its own, drops down to 0.9 psi whenever it feels Ike it and then will rise back up to 130psi and stay at 130psi for any given time then it repeats the process over and over.
Correct me if I'm wrong but the def pressure should hold psi and stay im excess of 130ish psi?

Its like it won't even build pressure with the key on.

The def level indicator light on dash comes on and goes off randomly.

The def level and the def fluid pressure are these wires tied together?

My actual def guage on dash always reads full and seldom does it ever read below full

Another thing I find strange is the aftertreatment def fluid tank temp doesn't seem to ever get hot, going down the road it 46 degrees, it is currently 34 degrees out

The coolant lines running to the def sending unit, the orientation of the coolant lines does it matter? I followed the coolant lines back to the frame rail where there is a coolant valve with an electric connection.

I have too many weird things going on with this truck currently

I believe my def sending unit is creating most of these issues, the def pressure is showing 130psi and I have check engine lights flashing, active codes
3596
3574
3714
3712 as inactive currently
Def sending unit was replaced in September and haven't really had any issues since then