I too am currently having an issue with my stereo not recognizing Grom Ipod Interface.
I have a 2002 Lexus ES 300 and according to their sales rep, the model is supported.
Unit came in yesterday and I plugged them exactly like the their formal instructions and posts here(thanks to couple of walkthroughs from Sonnet and Honda).
I also executed a couple of troubleshooting steps like replug all connections and switch on/off ignition many times to no avail.
When I pressed CD, I can hear quickly the audio playing from my Ipod(I set my Ipod to play some music) but it will immediately revert back to radio in less than 3 seconds.
So currently, I'm waiting for a reply from their support tech.
Many thanks for the community here. If this product works as advertised on my stereo, it would be totally awesome.
Samuel