ECM Code Reader

The MBE is going to be tough if you don't have a dash display that can read faults. Do you have the digital odometer in it? If so, you should be able to use the mode button to toggle to the fault codes. But with no warning lights coming on, you probably wont have any faults. Could be a lot of things that make it shut off, but check power and grounds in the battery box, check that all connections at the fuse panel under the hood is good (the main power comes loose on those), and check the fuel panel in the dash (lots of problems with the mounting breaking and loose fuses on those). They're a few common issues with the Sterlings in those years.

For your Cat, to get fault codes, have the cruise on/off switch "Off", the hold "Set" or "Resume" for a few seconds. The check engine light will flash active faults.

On the Detroit. Press the shutdown override button and the Red lamp will flash active faults, the amber lamp will flash inactive faults.