It really depends on the exact ECM you have, some ISB CM800 series ECMs are capable of limited onboard diagnostics (a diag switch, or at the very least grounding a pin at the ecm) and some are not.
in either case, your best bet is still to find someone with a scantool, or better yet someone with a com adapter and cummins insite software.
Being a soft code theirs likely nothing to worry about, but its still nice to have a scantool or insite to be able to have some more diagnostic information rather than just an XX code.
Not familiar with the coach, but most manufacturers put a engine diagnostic switch on the firewall under the dash, generally an ABS diagnostic switch located with it if its equipped.
FYI, if its a ISBE2/3/4 CM850 type ECM, its pin 2 of the OEM connector (smaller 50pin rectangular plug) on the ECM that you ground to enter diagnostic mode.
if you have the engine serial number handy i can get you a little better (specific) info
'14 XLR 395AMP
'16 Ram 3500 DRW, 6.7 cummins w/aisin trans and 4.10 gears