6G Celicas Forums

First off, let's clear up a few terms. It's OBD1 and OBD2, which stand for On-Board Diagnostics. OBD1 was implemented some time in the 80's and was used through 1995, when OBD2 became a federal mandate for all vehicles 1996-present sold in the US.

OBD1 cars, at least Toyotas, don't have an OBD1 plug per say. You use the Diagnostics connector under the hood. Maybe you're calling that the OBD1 plug? It's designed to short specific terminals which put it into diagnostic mode, then you watch the number of flashes on the instrument cluster. These flash pairings create a 2-digit code that you decipher from a chart. Yea, it's a bit more effort than OBD2 diagnostics.

One interesting thing I read somewhere is that certain Toyota/Lexus models from 89-95 also provide live data streams of certain sensors through this port. I tried connecting a scan tool with the OBD1 adapter hoping to pick up this live data once, but didn't get anywhere. The scan tool wouldn't even recognize the vehicle/ECU. Not having enough experience with OBD1 systems, I wasn't able to get anywhere unfortunately. Most of the guys that worked on these back in the day are long retired and out of the game by now, so it might be tricky getting any help.