[Elecraft] Airplane instruments issue

[Mike Short]

My son has a Piper Cherokee and recently installed a
Electronics international cgr30p monitor system. It worked fine for several
months and has now started randomly reporting impossible results for engine
temperature, fuel flow rates considerably higher than pump can deliver,
etc.

The wiring harness inside and the monitor have been replaced or verified by
the manufacturer. He has a breakout box that allows shutting off individual
data lines. No provision to monitor lines though.

 would like to monitor the DC bus and see if there is an AC component being
injected somehow. I would like recommendations for a USB oscilloscope that
would be suitable. I also have a RF explorer 50khz to 960MHZ that I could
use to monitor radiated noise.

Can anyone help me with this?

Mike
AI4NS