[hypoxia]

I drained the DEF tank (1/4" Allen Wrench), unplugged the electrical connectors and DEF hoses, removed & plugged coolant hoses.  There are two straps holding the tank in place, I cut those and removed the tank.  There are two small 1/8" Hex head fasteners that hold the DEF Head in place with a metal ring.  I removed the ring and pried the DEF Head up using flat screwdrivers and removed it.  It is held in place with an "O" ring.  There was a lot of dirt & grit in that recess above the "O" ring and some fell into the tank which had to be cleaned regardless.  The tank & DEF Head were spotless, no crystalized DEF or anything.  I pulled the Level/Temperature Sensor 960-0111-12 off & looked for a replacement, no joy.


I went back & looked up the fault code I had in Mexico, it was 3497 Aftertreatment 1 Diesel Exhaust Fluid Tank Level-Data Valid but Below Normal Operating Range.  I then read the Cummins Service Notes when they replaced the SCR 3 weeks earlier.  


Technicians notes  "I WANT TO EMPHASIZE DURING THIS REPAIR THERE WAS ZERO ACCESS TO ELECTRICAL SENSOR JUNCTION CONNECTOR AS IT WAS LOCATED ON TOP OF SCR.  TIGHTLY BOXED IN WITH WELDED PANNELS.  I HAD TO REMOVE SCR MOUNTING BRACKETS WITH TWO TOTAL AND USED A TRANS JACK TO LOWER SLIGHTLY BEING CAREFUL NOT TO RIP CHASSIS HARNESS I HAD TO USE A LONG PICK AND ANGLED LONG NEEDLE NOSE TO RELEASE LOCKS AND DISCONNECT ALL ELECTRICAL CONNECTORS BEFORE FINALLY LOWERING THE REST TO THE WAY. TO RE-INSTALL I USED THE SAME METHOD IN REVERSE."

Then I read the Level Sensor Testing Instructions "The Level Sensor must be tested while in the vehicle wiring, while the vehicle is running, because the Dosing Unit completes the output circuit of the Level Sensor. A simple volt meter across the yellow and black leads will correlate to the DEF’s level, while a volt meter across the red and black leads will correlate to the voltage being supplied to the unit"

I came to the conclusion that the most suspect item is the wiring that the tech had so much trouble with and probably not the sending unit.  More to come.....