For my '95 E320 I made one from an LED, a push button, three banana plugs and a plastic box. But you have to know how to count the flashes. I understand that some mechanics have a problem with that. My cousin could count to ten using his fingers; and when he took his shoes off, he could count to 22. That is, until he had the operation: They removed the extra toes because his shoes didn't fit. It also made that he could now only count to twenty.