Master warning light, check engine, variable others

Yesterday I started my car and got a series of warning lights across the dash:

1) Red Triangle - Master Warning Light
2) Orange (Symbol)CHECK - Malfunction Indicator Lamp
3) Orange (!) - Brake Warning Light (but it didn't highlight the word 'Brake' in red)
4) Orange VSC - Vehicle Stability Control Warning Light

Drove car across parking lot. Stopped and started it a few times, got the same warning lights.

Stopped and started it again, and the brake and VSC lights were gone. Only the master warning light and check engine light remained.

On the screen was the orange car icon with the ! symbol.

I drove the car home safely, about 4 miles at 45mph or less. The two warning lights stayed on.

This is a 2004 Prius with about 180k miles on it.

Any ideas on what the issue is? Do I need to take the car in right away?

 

Went to auto parts store, and they ran a diagnostic (I think that's what it was called -- plugged a handheld computer into a slot beneath the driver side front dash. Both messages that came up were for the hybrid battery.

How long do you think I can keep driving with those warning lights on? I'll have to drive to a repair shop or dealership.

 

Nope. I'll be paying someone to help me with this!

Question: do dealerships usually offer free diagnostic testing? I'm going to a reputable repair shop rather than the dealership, and their charge is $110 for an hour of diagnostics.

 

Thanks for your feedback. I appreciate it.