95 SLS Not going into overdrive

I have a 95 sls. The tranny is not shifting into overdrive. I pulled the codes 29,36,86 and 94. I know the 29 is trans axle shift solenoid B and 94 is the speed sensor. I'd like to test the trans by overriding the PCM but I do not have instructions for this procedure.Could someone help me with this. On another note, when I pulled the codes ,when it came to pcm,There was a question mark,PCM?. It would not scroll past this. I never came to a screen that said clear codes,Which is what I want to do. Any help would be appreciated. I changed fluid and filter this am and everything looked clean.I' sure the tranny is not bad.

Thanks
Mike