DEF Wire Connection Problem?

I had a similar problem on one of my def heater lines this winter. At first they changed the whole heated hose. But it turned out to be a corroded wire on the one-box side of the same connector.

 

Yeah you can check for continuity. The troubleshooting tree you posted looks like a pretty solid start. Testing for voltage between pin 4 and ground followed by the next steps to help isolate wether it’s a wire or the unit itself. The truck wash could be a clue too, and would lead me to inspect real closely at anywhere that was pressure washed. Especially if you got a motor wash. It’s real common for folks to pressure wash to hard around the ECM, sensors, harness, and introducing water behind firewall electrical pads throughs

 

So it sounds like you have an open or scuffed wire between the metering unit heater and the ACM. I would follow the harness back from the metering unit and the ACM. I would start opening the loom to look deeper where ever it makes a bend. If all else fails you know what pins to connect. Run a new wire from the ACM to the metering unit heater.

 

No, the ACM aftertreatment looks like the MCM bolted on the side of the motor.

If it’s like the Cascadia is anything like the Coronado. Then the ACM is mounted in front the air tanks/ battery box, with a plastic cover, right behind the left steer tire. (Yeah like the dumbest f’n place to mount such an important computer, like nothing would comes off the steer tire and hit it.)

At the ACM the large bundle of wires comes off both the 21 pin (com/power) and 120 pin (sensor) connectors travels up the frame rail over to the top rear of the tranny, splits off the communication/power, splits off for the def pump/tank/line heaters, and sends still a large bundle of wires to the OneBox sensors and metering valve.

On my trucks, we usually have wire troubles right on top the one box and above the ACM, though we have had a few ontop the transmission and more over around the def pump, but your issue will be inline between ACM and onebox.

 

Your arrow is pointing to basicly a box that holds the NOX and exhaust pressure sensors

 

Does your dash display a FMI or FAIL number with the code?