All right, try this: solder two LEDs in parallel, the long leg on one to short leg on the other. Add a 1k resistor to one side and a length of wire to the other. Now you have an RS232 tester. One LED or the other will light when you connect one wire to ground and the other to the pin in question, if it is powered. If data is being sent you will see a LED blink. OR even if the pin changes you will see it.
Paul