The Murphy IX3212 PDM has output diagnostic capability to let the user know if there is a short/open-circuit or an over-current. 

See the following sections of the attached manual: Current Limit – This sets the overcurrent shutdown level in 2.5A increments (see next line below…). Auto reset function – This sounds like it will force the output off if it encounters a certain number of overcurrents. If this happens, the output needs to be commanded off before trying to use the output. Output Diagnostic – The unit can tell you if there is, among other things, an overcurrent

4.5.5: Current feedback info – 0.125A increments

If the output is not responding, check for an over-current (or other error) state using the PGN described in section If an error was detected, send an OFF command to the output and then try to command it again. Even if it does not show an over-current, try sending an OFF command to the output before using it.