If a CERF certified shop fixed it they guarantee that it will pass, that is the point of certification.

Then why does the MVA give waivers?

There's a lot of interesting videos on youtube about OBD2 testing. Some examples:

Emissions Test - What are I/M Readiness Monitors And How To Fix

Make your car smog ready in 15 minutes - I/M Readiness Drive Cycle Procedure

You would think, but Doesn't appear to be true. https://2019-mde.maryland.gov/progra...Fs-Locate.aspx

I'm not going to say it's a scam. But I would bet that there is a fee paid to the state by every shop on the list. Similar to the Top Teir gasoline certification.

Drive cycles are not generic, a good shop can print the drive cycle procedure specific to your vehicle.

Sorry Advance Auto parts scanned and told you it was something about the oxygen sensor. Then you took it to rising sun?

2 years ago, I could not get the I/M readiness monitor to complete the Catalyst test. No check engine light, no codes. My good mechanic thought from the live data, that it could potentially be the oxygen sensors, which were original to the vehicle. Replacing them didn't help. I took off the 2 year old catalytic converter, and reinstalled the original, and the I/M Catalyst test ran soon after, and I passed smog.

The OBD2 system helps an experienced, trained mechanic to find the cause, but there are often several potential causes for any particular code. But in my case, didn't e even have codes to help, just the status of the I/M monitors. Sounds like you might not have codes either.

There's not a lot of difference between all the cheap code readers. Look up OBD2 code reader on Amazon, find one with good review. Make sure it will provide the I/M status.

The FOXWELL NT201 is on amazon.com for $35.98. Free delivery for orders over $35. I'm going to order a reader and see if I can see what's wrong with the car. At least I can tell if its ready for the emissions test.

Foxwell NT201 OBD2 Code Reader Review And How To Use

You would be much better off getting a scan tool rather than a glorified code reader.

If you spent $450 or more to get it fixed you should have apply for a waiver.
The retesting that you put off would have been free.
Certified shops are supposed to have testing equipment so that they can be sure you pass.
Cars built 1995 and before are exempt. OBD2 was mandated in 1996.
If you bother to read this; here is the Maryland rules: https://mva.maryland.gov/vehicles/Pages/veip.aspx
I guess it much easier to worry about things than to just ask the authority.

My turn to say your link is 404, RJ.

How odd, just followed a Google search result, then shared... oh well, here's the copy and paste.

Maryland Certified Emissions Repair Facilities (CERFs) employ skilled Master Certified Emissions Technicians, who have earned the highest national recognition for expertise in emissions repairs.
Motorists should consider that specialized training and experience may be necessary to perform effective emissions repairs, but motorists are not required to have repairs done at a CERF.

IDK about that particular model, but there are Foxwell that are a lot more than code readers.

I've heard of Foxwells being used to pairs fobs and a bunch of stuff you thought you needed a Tech II for. I thought Foxwell claimed to was pretty much a Tech II. Now I wanna go back and check. I do recall they have several models and it's importand to chose the right one, depending on your car(s.)

Tech2 is just a computer that runs the GM proprietary software. You can "obtain" the software.

https://mde.maryland.gov/programs/ai...erflookup.aspx

I'll ask the people at the emissions station about this. I placed the order for the Foxwell reader Feb 9 from amazon.com and got it today. I haven't tried it yet.