The dash gauges not working will not cause a smog check failure. The only indicator (light) on the your Toyota Sienna which could cause it to fail the smog test is the Check Engine light or MIL (Malfunction Indicator Lamp). With the problems you've described however, we highly recommend you make sure that in fact the check engine light is not illuminated. Also, it is quite possible that due to the drivetrain faults certain emission monitors have not been able to run and are not in Ready (or Completed) status. If any of your Toyota Sienna's emission monitors are not ready (except the EVAP monitor), your Sienna will still not pass the smog test... even if the check engine light is not on. Our recommendation is that you have a smog check certified auto repair station diagnose your Sienna's problems before the smog test.
