2001 subau high beam lighton when lights on

It could be driving lights mode instead of low beam. Check connections.

Suspect dip switch requires renewal

High beams are on by pulling the lever toward you temp mode to engage the high beams simply push the lever forward the high beams should engage then.

If your high beams are controlled by your blinker lever if you pull.the lever towards you it will flash the high beams on. If you push the lever towards the front of the vehicle(dashboard) it should stay forward. Click it back towards you it will.go back to normal lights

Most likely the instrument cluster is bad. As long as the high beams are working than the instrument cluster led driver should be getting the signal through the computer data line that the high beams are on. The led driver than grounds the circuit to illuminate the high beam indicator.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

The daytime running lamps in your 2001 Chevrolet Impala are controlled by the Body Control Module (BCM) Here is a description of how the system works:

The ambient light sensor is a light-sensitive transistor that varies its voltage signal to the Body Control Module (BCM) in response to changes in the outside (ambient) light level. When the BCM receives this signal, the BCM turns ON either the DRL or the headlamp relay for auto headlamp operation. Any function or condition that turns ON the headlamps will cancel the DRL operation.
Thirty seconds after you start the ignition with the headlamp switch set in the OFF position, the DRL will perform one of two actions:

Illuminate the high beam headlights at a reduced intensity in daylight conditions
Illuminate the low beam headlights in low light conditions
The DRL/EXT lamps fuse in the top of the engine fuse block supplies battery positive voltage to both the DRL switch contacts and to the DRL relay coil. When the BCM energizes the DRL relay coil, current flows through the right high beam lamp, to the left hand high beam lamp, to the energized DRL relay switch contacts, to ground G101.
The high beam headlamps are now in series, and split the voltage so that the headlamps illuminate at halt intensity. The DRL operates when the ignition switch is in the RUN position, and the parking brake is not set or the transmission is not in park. When these conditions have been met and the ambient light sensor indicates daytime conditions, the DRL will illuminate.

Same thing happened to me when I switched to brighter bulbs, indicator back to normal after switching to stock bulbs

First check both side head / dip light bulbs as a faulty bulb can cause the problem you describe
Best of luck
John

you likely have the wrong bulb in the headlight

Most likely a bad headlamp switch, UNLESS you have a remote starter hooked up. Corollas with a body computer really do not like remote starters, they cause really bizaare things to happen.