GMC Troubleshooting Questions? Ask a Mechanic for Answers
You should be able to scan the BCM to see if turn signal switch is sending signal for turn for right side. The problem sounds like it is not signalling BCM. The Brake and turn signals are separate circuits into the BCM and the BCM turns on the correct lights. Do you have wire diagram of circuit? Let me know if you need it?
"I hope that helps! My goal is your satisfaction today. If you feel I've been professional and helpful, your 5-star rating at this time is most appreciated. However, if you still need my help, you can hold off on the rating for now and reply back here -- I'll respond as soon as possible! Thank you"