There isn't one. The old three-dollar mechanical flashers didn't cause any trouble so they went to a 50-dollar electronic flasher assembly. That still wasn't unreliable enough. Now the signal switch sends a voltage to the Body Control Module under the dash which sends a signal to the Integrated Power Module under the hood. Magic takes place between them and the signal lights flash. Two computers to make the signal lights work. That rivals Ford's use of two computers to make the horn honk. If it sounds like I'm being sarcastic, you're right, but it's why I refuse to give up my rusty, trusty '88 Grand Caravan. 25 years old and the flashers and all the signal bulbs are still the originals, and it's my daily driver.