I am always on the hunt for novel special tools for my 1990 Miata. I've come across an engine signal monitor which is basically a fancy multi-meter that sits inline with the ECU by way of a special adapter harness. My chassis service manual calls for p/n 49-9200-162, and this particular unit is p/n 49-9200-162A. Based on my research, the "A" version of this tool came into service in 1994. My question, is the "A" unit backwards compatible with models prior to 1994? The infinite monkeys of the Internet appear to have never been asked this question, I turn to you with the most obscure question ever asked of The Answer.
