Bringing up an old thread that looks like it never got any reply.
I was able to get into the diag screen by holding the top center of the nav screen for 7 seconds after hitting the menu button on the main nav screen. I then put in code 9448. I was able to see codes, but have been searching the web for codes like
Then they went to OBDII ? They have to have it. That is how we do state inspections. They plug into the ODB and start the test . I am going to pick up a code reader / reseter soon, I just didn't think I had to as the diag screen had codes and a way to reset them. ( it should for the money )
Those codes are meaningless, probably some engineering stuff for the radio.
OBD-II was born in '95, full implementation in '96. That has nothing to do with DIC code retrieval, moreso to do with engine control diagnostics in general.
The on board stuff with the climate control head and DIC controls stopped in varying years depending on the car.
'05 and up STS has no such capability.
'06 and up DTS does not either.
CTS never had it, although I think I have heard some guys found something.
It is a thing of the past really. You need a code reader or a scan tool to accurately retrieve diagnostic codes.