Need help with a used 2004 Cadillac CTS 3.6l ECU

[Great-Kazoo]

What does the smog place says is the reason you failed?

[DFBrews]

Anyone out there with a scanner that can help me find out why my new car is having issues. I can't get it to pass the internal smog test to get it ready for Emissions test.
I was hoping someone has access to advance scanner like a Tech 2 or similar that can help me find out if the computer is bad.
The car's temp and gas gauge don't work. The gear shifter light doesn't light up and the reverse lights don't work either. I think they are all related to the ECU since I reset it and all those things worked for a little while. I was hoping to get it reflashed if it was done wrong the last time. The former owner changed the ECU and I'm not sure it was done right.
Thanks in advance. Of course I will pay. I'm just hoping to avoid the dealership fees for a car of this age. And I want to get someone that cares a little more than a run of the mill garage that will take your money but might not earn it.

What does the smog place says is the reason you failed?

they can fail based on emissions related OBD systems not being online or not having run their internal diagnostics

[Great-Kazoo]

they can fail based on emissions related OBD systems not being online or not having run their internal diagnostics

Right. However until one knows why it failed, guessing is just that. Did it fail for something simple, or will the new car repairs cost more than the OP wants to invest.