The gear change solenoids (S1/S2) sometimes go bad in early transmissions. When they do, symptoms are erratic poor shift behaviour and/or 'missed gears' and of course fault codes. In my case, this was caused by poor internal soldering in the solenoids - easily fixed, if necessary. I had a spare trans and just shifted parts out.

Haven't examined any lockup solenoids, though. They look different but could be reparable, too. Worth checking before replacing at that cost. The bad thing is that you've got to take the trans pan down for inspection, not that funny on a 960 (glued gasket). Replace with an aftermarket regular gasket when/if you do it and replace the filter as well when you get in there.

Martin
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'65 121, '73 165