When power is applied to the I/O housing after the J890/J892 interface module has been installed in the drop, the module performs a set of confidence tests on itself. If any faults are detected in the RIO processing portion of the module, the RIO LEDs on the front panel will display a flash pattern of error codes.

The interface error (OBM) test may be caused by an I/O module that has shorted the I/O bus. All of the other diagnostic error codes indicate an internal failure in the remote I/O processing portion of the J890/J892 interface.