I have been asked for a simple way to test the various XIED's so riders can verify they are working correctly.

The failure rate on XIED's is less than 0.05%. I have had IED's returned to me that were burned because of contact with the exhaust system that still passed QA testing. So the manufacturing process for the IED's is very robust. The Nightrider QA test procedure for the various IED's is done by applying voltage to the O2 sensor end of the IED and measuring the voltage that the ECM would see. We have a test set to perform this test, something that most riders will not have.

So here is a test that only requires a VOM set for measuring the resistance between the opposite ends of the IED connectors
Grey to Grey will have a resistance reading
Blue to Blue will have no resistance but you do have continuity
Blue to Grey will have a resistance reading

Any open reading  or no continuity would indicate the internal connections might have broken.

Resistance readings can be anywhere from 8k to 25k depending upon the version of the IED you are testing.
The Blue wire is constant on all IEDs. The Blue wire is the positive side of the sensor signal.
The Grey wire may be a different color on some variations to indicate the type of IED if there is not a center band.
Grey/Blue with center band can be XiED, X14iED or ViED
Grey/Blue = O2 IED
While/Blue = DYN OiED
Yellow/Blue = XiED