Had exactly the same problem, 2000 Prizm driver's side front fender bender, had to replace the left directional/running light assembly, bang out fender, started blowing tail light fuses(15A), which of course knocks out the instrument panel lights as well.
After much circuit tracing, the problem turned out to be in the new bulb holder fixture in the new directional light assembly I bought from Rock Auto. If the wiring harness connector isn't pressed far enough onto or into the fixture that holds the bulb, something in the fixture shorts out the internal copper leads that power the running light from the green wire that feeds it from the wiring harness. Did it with the old fixture as well - the clearances in the bottom of the fixture under the bulb seem to be pretty close, and maybe that allows the short to happen. It will also short out if you remove the bulb while the tail lights are turned on. Know this sounds weird and improbable, but that's what I found.
The easiest way of troubleshooting this(rather than going through a pile of 15amp fuses) is to take a blown fuse, nibble away at the plastic ends enough so that you can solder a wire to the two tabs on each side, which when brought out will give you a way to measure current(if you like) or, better yet, to attach a 1 ohm 10 watt power resistor between the ends of the two wires from this made up fuse substitutor/circuit tester. Then if you turn on the lights manually and leave the car door open, the warning buzzer will sound and the tail lights will dimly glow. If there is a short, the resistor will get hot and the tail lights, etc. will not glow. Don't replace the fuse with a higher amp one or short the two wires on this made-up tester together, or you can do serious damage to the wiring and the relays in the tail light circuitry, which could make a relatively simple repair into a significantly expensive one. Tracing out shorts in the tail light circuit is a real challenge because it powers so many bulbs and devices, and this means of testing for shorts can really help.
After much circuit tracing, the problem turned out to be in the new bulb holder fixture in the new directional light assembly I bought from Rock Auto. If the wiring harness connector isn't pressed far enough onto or into the fixture that holds the bulb, something in the fixture shorts out the internal copper leads that power the running light from the green wire that feeds it from the wiring harness. Did it with the old fixture as well - the clearances in the bottom of the fixture under the bulb seem to be pretty close, and maybe that allows the short to happen. It will also short out if you remove the bulb while the tail lights are turned on. Know this sounds weird and improbable, but that's what I found.
The easiest way of troubleshooting this(rather than going through a pile of 15amp fuses) is to take a blown fuse, nibble away at the plastic ends enough so that you can solder a wire to the two tabs on each side, which when brought out will give you a way to measure current(if you like) or, better yet, to attach a 1 ohm 10 watt power resistor between the ends of the two wires from this made up fuse substitutor/circuit tester. Then if you turn on the lights manually and leave the car door open, the warning buzzer will sound and the tail lights will dimly glow. If there is a short, the resistor will get hot and the tail lights, etc. will not glow. Don't replace the fuse with a higher amp one or short the two wires on this made-up tester together, or you can do serious damage to the wiring and the relays in the tail light circuitry, which could make a relatively simple repair into a significantly expensive one. Tracing out shorts in the tail light circuit is a real challenge because it powers so many bulbs and devices, and this means of testing for shorts can really help.
