Mine did the same...bad wiring harness. What was happening on my rig was the engine would stumble at times or completely shut down but then start right back up. This happened over the period of several months. When I sent it in for repair I had SMB do some other work prior to replacing the harness by a diesel shop. One of the SMB techs got the privilege of having the engine shut down at 65MPH on the highway
. Before that, the engine had usually just cut out for a second at high speed or died at slow speeds from time to time. It never left me stranded but it was nerve racking especially on one off road adventure
waiting for a complete shut down. Luckily it never left me stranded. BTW there was no CEL or any record of issues with any engine codes which I thought strange. I didn't like throwing money at a guess
but I figured being close to 90K on the engine it would be part one of the bullet proofing. I also had a bullet proof FICM installed. The shop thought the FICM was good but I had been wanting to upgrade it anyway. They did give me the old harness and showed me where it had rubbed in spots and other sections that were brittle.
I had a new harness installed (later heat wrapped) and hood louvers installed to help lower the heat (hopefully) in the engine bay. The shop doing the wrapping is in Fresno called J's Performance Diesel.
No mechanic here and I'm not saying this is your problem.