The 'off' position turns on the "day time running lights", which happens to be the headlights. The instrument cluster lights should not be on, the high beams cannot be turned on, nor will the fog lights work.

The middle position is for parking lights only.

The far right position is to turn all of the lights on for night driving.

There is a dealer programming option to disable the DRLs, but most dealers do not like to do this and will charge you an hour's worth of labor.

Your light switch is not unique to 2003. I think it started back in 1994.
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Keeping it running is better than buying new