I have a very similar issue with my 1997 ES300 Lexus (I'm the original owner). 3 days ago I went to get a smog done but failed because of no OBD signal communication during testing (a first). The car is a low mileage (110) and previously had passed all other smog testing(last passed 2yrs ago). Vehicle gets its routine maintenance fluids/oil/ filters, belts, wipers, brakes, transmission/radiator flush and new battery to name a few but never had any major mechanical repairs or modifications performed on the car. Aside from this current issue the car sounds and runs fine. Never experienced dashboard lights or a check engine light. I have done some online reading a common problem seems to be the cigarette lighter fuse but both of mine work since I use them to charge my cell phone and Ipad on daily basis.

When I get home, plan on doing a visual inspection of the DLC for an bent or damaged pins. I also read something about the OBD fuse that could also cause this problem. Any help is greatly appreciated before I have to visit the dreaded dealership.

Mark what brand of OBD reader did you use?