Lots of times the FSM shows the use of a SST diagnostic device.
Not the tools but a plug in device.

My local dealer doesn't have the old ones that the FD used.

Just curious if these are available from anywhere. Perhaps it was a model that worked for more than one brand of car?

Anyway, seems like it would be handy to have.

 

I know you don't need it to pull codes, but the FSM uses it for checking lots of other things like ABS diagnostics etc.

 

The ABS has its own diagnostic codes as well (flashing airbag light), you don't need the SST there either.

 

For the most part this tester just grounds out certain combinations of pins on the diagnostic connector and/or counts ground pulses to read codes. There are alternate ways to read codes.

This is typical for an early 90s car. A lot of those old scantools had memory cards or other such things inserted into them for each vehicle. They tend to crap out eventually and the manufacturer stops supporting them.