2005 Toyota Camry. When car is going about 40 mph everything is fine. However, as I decelerate my gauges go off and radio turns off. Engine still runs and as I accelerate back to 40, everything is working again. Checked alternator, only putting out 9-10 volts, so it was replaced. Put car back together, same issues. Car will not go out of park, no gauges or radio. At start up the gauges, radio and shifter work, but it’s a matter os seconds before issues start again.
Your battery could be loose in its mount.Make sure its tight and cable connections are solid.
And check all the grounds.