what is the make and model. You may have a harness connector up near the firewall that you can do a pinout test for the solenoids.
I Checked one in a jeep a little while back and I was able to ohm it at a breakout connector at the firewall . Never had to crawl under.
Most of the coils are 1.1 ohms. Seems one is a different value ( i think it was the lockup solenoid)
I had one solenoid come in at .7-.8 ohms it was the culprit. Changed the pack in the trans in about an hour and a half.Works perfect again.
Post your make and model with engine size and I will put up some info for you.