Hi, Elliot before diagnosing any turn signal/running light/parking light issue make sure the bulb is good and the light fuse has continuity with a test light. If you have replaced you OEM lights with LED lights you are going to need a load equalizer. If no turn signals work the cause could be a faulty turn signal module or the connector going to it, look for corroded, loose, or broken pins/sockets. Contact spray cleaner is great for removing corrosion. If your speedometer does not function properly it will have to be fixed first because your turn signal module gets the data from the speedometer for normal turn signal function. If your front turn signals don't work use a test light to check for power and ground at the bulb socket, then start backtracking the wiring through every wire connector to the turn signal switch/button and check for continuity, go all the way back to the fuse if necessary to find the cause of the malfunction. If your rear turn signals don't work check your rear fender wiring harness connector first for corroded, broken, loose pins/sockets, power, and a good ground, (the harness connector is usually located under the seat on the front of the rear fender) then keep tracing the wiring look for obvious harness damage caused by the rear tire. If you still can't find the malfunction backtrack from the rear fender wiring harness connector. If one side does not work you could have a faulty turn signal switch or module check for continuity.
Before diagnosing any brake light issue always check the bulb and fuse first for integrity a brake light staying on is usually caused by the front brake light switch, which is mechanical, not disengaging. On early models moving the throttle control housing closer to the front brake master cylinder is the main fix. On late models, the switch gets tweaked and needs to be realigned. A brake light that does not come on when the brake lever is applied can be caused by a faulty switch or no continuity in the wiring at the switch. The rear brake light switch is hydraulic and it is extremely rare to malfunction in a closed circuit condition causing the brake light to stay on. Usually, rear brake light switch issues are caused by no brake pedal free play or a sticky rear master cylinder piston. A brake light that does not come on when the rear brake pedal is depressed can be caused by a faulty switch, air contamination in the brake line, or no continuity in the wiring at the switch. For more information about your issue and valuable "FREE" downloads that you will need please click on the links below. Good luck and have a nice day. http://www.starmotorcycles.com/assets/service/manuals/2003/LIT-11626-16-05_22.pdf
OEM parts for Yamaha