I have a 2001 GMC Yukon xl 4WD, with a blinker problem. The clicking, blinker sound stays on even when the blinker is off. When I do use the directional, it works correctly.
But when it should shut off, it continues to make the clicking sound even though the blinker lights(outside lights) are not blinking. It also comes on by itself and shut off by itself.
This happens frequently but in no particular pattern and lasts no particular length of time.It can last seconds or even minutes before shutting off (or driving me crazy.) The problem started a couple of months ago and seems to be happening more often now. Also, (I believe this is unrelated,) but occasionally, while I am driving, my brake light and ABS light come on at the same time and go off eventually. This occurs less frequently than the blinker problem, maybe a couple of times a month.
I had the same problem with a 2000 Blazer, I had to listen to the blinker for 5 1/2 hours stuck on I-95 coming up from Wash DC. I had to replace the multifunction switch (turn signal, cruise, wipers, etc). You can try spraying some CRC Electrical Contact Cleaner into the base of the switch at the steering column. This helped for a couple of days, but I still had to replace the switch eventually. Perhaps you will be luckier. The switch is around $200, not counting labor (~2 hrs).
As for the ABS/Brake light, it could be a sensor at one of the wheels, make sure all the connectors are secure and clean. Also check the level in the master cylinder, especially if the light appears while braking or turning.
Good luck,
Ed B.
This is a guess: faulty flasher unit or perhaps not grounded properly.