I was having a check engine light issue, I changed o2 sensor. Now speedo stopped and tranny won't go if not in 2nd. Changed vss and no change. HELP me please!!!! Need to pass inspection. 06 trailblazer 4wd 4.2. engine.

What are the codes?

Check for codes please.

Yes, agree with the others ^^^^^^^ : Codes please.

Also:

How many miles on it?

How long have you owned it?

What region does it live in?

Has it suffered any major trauma recently?

Did the speedometer stop working immediately after changing the oxygen sensor? . . . or were you able to drive for a bit and then it failed?

Need to scan all modules NOT just the PCM which is what most code readers do.