P26 ab Code 3 way coolant valve stuck Loss of supply power

[BigMilly]

I own a 2016 Ram 1500 eco diesel, i changed my 3 way coolant valve in June 2023 and all
Codes cleared, but recently the P26 ab code came back up. Does anyone have a wiring diagram or know where or why I would have no supply voltage to my 3 way coolant valve? I checked pin 1 on the 6 pin connector to the coolant valve and it has 0.2 volts when it should be 12 volts dc. Pin 1 F947 pink/lg is the IGN RS Supply to the valve motor. Pins 5 K900 db/dg and Pin 6 Z908 black are both grounds and test out fine. Pin 3 F856 yellow/pink is 5volts dc supply which is fine, and Pin 4 K473 orng/yel is the coolant valve signal voltage which tells the PCM if the valve is moving or not. I had a steady 3.2volts at this pin when moving the heat up and down in the cab with ignition in the run position. I traced the wireback to the large 10 pin connector just in behind the front bumper passenger side. Same thing at this connector. Took it apart, tested the same supply voltage pin and .2 volts is all I get. From there it goesup into a larger taped up wiring bundle and appears to go to the PCM or ECM. im thinking that supply wire must go to the fuse panel and not to the PCM? does anyone have a wiring diagram or can anyone tell me where the supply is sourced from? thanks for any help in advance, Matt

 

[BigMilly]

Went into the dealer to
Verify this diagram as well. Looks like pin 1 is the fused ignition run/start control output which Im assuming is constant battery power when truck is in the run position.

 

[BigMilly]

Sorry this has taken a bit of time. Just juggling family and work then in trying to trouble shoot this issue. So as a recap, 2016 Ram eco diesel. I
Changed the 3 way coolant valve in June 2023 replaced with mopar coolant valve. In November 2023 the Service 4WD light came on intermittent, then stayed on solid. With in minutes the check engine light came on. i read the code and is was P26ab 3 way coolant valve stuck.
i tested power to the coolant valve on pin 1 of the connector and supply was 0 volts DC with ignition in run position engine off. i disconnected the 4 pin connecter to my front Differential 4WD actuator and tested for supply and had 0 volts DC with ignition in run position.
I traced the wires to the 10 pin connector just inside the front passengers side bumper and disconnected it. I tested power on the pink and beige pin and 0 Volts DC. Today I disconnected the 10 pin connector and pulled the bundle of wires up so I could unwrap the black tape and inspect the wires. Low and behold the tape was worn through and the pink and beige supply wire was severed. The ground was barked up a bit as well. It rubbed through on the metal frame but without taking the bundle up to inspect you would never be able to see it. I reconnected the wires and used heat shrink to seal the connection up. Taped everything and tucked it all back in. 4WD Service light went off immediately and I cleared the engine code and all is back to normal!! Hope this helps someone else out in the future. Power to the 3 way coolant valve is also power to your 4WD actuator.