How do i shut down the daytime running lights on a 2002 pontiac montana

Why would you want to disable them? They provide increased daytime visibility of your car to oncoming traffic. If they bother you for some reason, just pull the bulbs out of their sockets. That way they can be restored if you go to sell the vehicle.

Sorry, I missed that you said your lights were dim and you wanted to do this to troubleshoot the problem. Pulling the bulbs would still work for you. However, they probably are not the source of your problem. Dimming lights are more typically an alternator or headlamp relay problem. That's where I would start.