2011 Cascadia

I would think truck is shorting to power on one of the circuits. If you post the last six digits of your VIN we can help narrow it down. The Cummins wiring diagrams over here might be helpful Cummins Wiring Diagrams

 

SB5629 comes back as not valid serial number. Double check on that and also check on the top flange of left frame rail to the left of engine. VIN is stamped in frame there. Just the last six of VIN is all that is necessary.

 

Your engine is CM2250. Just looking at the ISX CM2250 Cummins wiring diagrams over in mechanics forum I posted before it appears from them power from ignition supplies Pin 3 of the OEM connector at the ECM. However, on that same circuit ignition is supply pin 52 of aftertreatment DEF controller at 53 pin connector. Outlet NOx sensor relay at pin 85 and and a sensor where it supplies 12 volt to pin C and other two pins of sensor go back to pin 58 and 59 of Aftertreatment DEF Controller connector. Appears 3 other parts of circuit could be feed power back to Pin 3 of OEM connector at ECM. That diagram should give you some direction.

 

Ignition circuit appears to be gray wire labelled 439A. Also, at Power_Train PDM Relay 1 pin 86 appears to be supplied power from ignition R1_86 and relay 5 pin 30. R5_30.

 

Sometimes a picture is worth more than a thousands words here. Here is a diagram of your wiring from BOM 283.


Here is the IGN KEW SW circuit on the CUMMINS ECM (not MCM).





This circuit is spliced and shares to the SAM CAB of the truck--very important to understand and not leave out.




Look right here at this connector, ENG_H_FW_EFW_1A, and make sure water/corrosion hasn't gotten into the connector.


Please report back your findings.