I installed a Sony XAV-AX8500 into a 2016 Toyota Highlander Limited with the JBL sound system using an iDatalink Maestro RR and their ADS-MIC1 factory microphone interface.
When on a call using Apple CarPlay and the engine off, the sound comes through crystal clear on the other end of the call. As soon as the engine is running, whether the vehicle is driving or stationary, there is a constant static/feedback noise that comes through on the other end. You can still hear the person in the vehicle's voice, but the static is constant.
When the vehicle is driving, a high pitched portion of the static noise does seem to fluctuate in relation to the engine rpms, but otherwise the overall volume of the static is generally unchanged when driving versus sitting with the engine idling.
Adjusting the ADS-MIC1's mic gain setting changes the volume of the voice on the call (as you would expect), but has no effect of the volume of the static.
AI says it's most likely a ground issue. Any ideas as to what the most likely culprit is, or how I can fix this?