Is there a way to set dash lights to auto dim?

No.

 

yes... You can do that...

simply leave the dimmer in dimmest position at all time unless it's get too bright out, but don't ever change the dim level = happy wife, happy life...

in other words the car was built a dozen years ago, it doesn't do more modern stuff...

 

I think you've got it backwards though... OP would need it set to override/bright just to read the displays during the day with the headlights on, which leaves the switch in the wrong position for night driving.

I know of no way to automate this without modifying the car.

Just curious- doesn't a 2009 have an automatic daytime running light feature for safety?

 

Lol, I do NOT have it backwards... The wife is right and we can't challenge her on this... Pick your battles wisely... Not being able to see a dim screen during the daytime hours is a small price to pay to keep her as happy as possible.

 

And another note:
IF......the car has a DRL positon or automatic daytime running lights....then THAT is the best way to drive in the daytime.
With the headlights ON, the tail lights are also ON and that makes your brake lights just a tiny bit less likely to be seen.
In some cases, it can be LESS safe to have them ON all the time.

As opposed to DRL, I can't see how full ON would be any better.
That is why the DRL function was created.

 

Not sure if it's the same, but 3rd gen, you roll the brightness dial up to just under the detent for brightest. Then it's bright in daylight, and auto-dimming as it gets darker. Click it through the detent (to brightest), then it stays full bright all the time.

 

I'm pretty sure that NO Toyota models have dash lights that automatically dim independent of the headlights.
But they ALL probably dim the dash when the headlights come ON......be that either automatically or manually.

 

Gen 3 Prius does if it had the auto headlight feature (or if it didn't but the owner adds the missing wiring to enable it). The feature uses the existing solar sensor that's already in the dash, and the ECU already knows how to do it, so only a couple wires and a switch are missing in the models that didn't have it factory.

To me, the way it controls the dash lights is worth the price of admission. I almost don't even care that it also turns the headlights on and off. But around dusk or dawn, having it turn the headlights on but keep the dash bright so I can read it ... priceless.

I do not know whether a Gen 2 body ECU has any of that baked in though.