1994 850 T5 Wagon Auto Trans Issue

[Bricked850]

As the title states, I'm having issues with my transmission.
I started my car and started driving, but my transmission was slipping. After checking the level, I added a quart of ATF and a bit of Lucas Stop slip, and it seems to be back to normal, but it does occasionally slip in 1st.
I also have the up arrow flashing (which I am aware is a transmission fault).
I'm curious about how to diagnose the light and possibly reset the computer (I tried to reset it by disconnecting the battery for a few hours, to no avail). Do I need to buy an OBD1 scanner or will the paperclip method work as well?

[Swedespeed96]

Have you tried disconnecting both terminals and touching them together for 30 seconds

[TheVolvoNut]

Your built in obd-1 system should give you a code to point you in the right direction. A1 is for the transmission, as well as A5, which covers the transmission control unit.

[Tonyfr]

Here is video for the codes - LINK

[05V70RGT]

I believe only 95 had the built in code reader but I could be wrong. Its been known to happen.

[Tonyfr]

1993 to 1995

[TheVolvoNut]

You beat me to it tony! We have a 93 auto-tragic with our volvo stash.