Should the “Cooling Performance of the Hybrid Battery is Low” warning stay on after cleaning?

Did you clean the fan and the ductwork leading to it? If you had that much link on the inlet filter, the rest is likely pretty snowed in as well.

See video 21 here:

Nutz About Bolts Prius Maintenance Videos | PriusChat

But do take a look at this first:

HV Battery Fan Cleaning | PriusChat

^ in a nutshell: no need to remove rear seat.

Also, you CAN clean the fan without removing it; just getting down to it, but leaving it plugged in and bolted down, you can clean it fine say with Q-Tips. Don't make more work for yourself.

 

Not sure. I suspect it'd go away after you've driven a bit, after cleaning fan and ductwork. Assuming that's the issue. It often is.

So the filter you cleaned is right at the seat back, at the air intake grill for hybrid battery?

 

If the fan is/was clogged, the battery may be clogged.
You might have to take the top off and blow out the battery, in reverse, toward the fan.
It could be blocked between the battery modules. That's why the warning won't clear.
Have you tried unplugging the 12v battery for several minutes.

 

Are you regularly transporting pets?

 

Afterwards, clear the DTCs to reset the learning values even if no DTCs are stored.

 

could be inside the battery too, how many miles on her?

did you check the fan connector for corrosion?