Any nominal OBD-II reader will not be able to read codes from the transmission. The transmission's CU is flashing those lights to tell you something is wrong with the transmission control system.

The number one candidate for fixing this is replacing the PNP switch located on the passenger's side of the transmission. Depending on clearances on you individual car you may need to loosen the exhaust pipes and/or the oil cooler line to change it out. There is rotational adjustment range in the switch mounting so note how the old one is oriented and try to match it. Since the switch controls the back-up light this can be used to help with the alignment also. See that the lighting function is centered around the "R" position of the shifter when done.

Other possible causes are poor contacts on any of the three connectors along the driver's side of the transmission.

Switch contacts can sometimes be temporarily fixed by working them several times. Try "Rowing" the shiftimg lever a few times as well as poking the "W"-"S"-"E" switches.

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'96 965, 16' wheels, Michelin Pilot Sports, rear 18mm bar + Koni, 201 HP cams, 149K. Put 200K on '85 745 TD.