The low idle voltage could be down to a low idle. These tachs can read 300-500 rpm high. No big deal, perhaps, at cruising speeds, but setting your idle at 1,000 rpm with the tach when that is really 500-700 rpm is not good.
Use Guzzidiag to confirm the actual idle and the "Decent Tune-up" for the idle procedure.
Good to keep an eye on the charging voltage. The Odyssey is not to exceed 15.0 volts.