Passing CA Smog Test?

[JPolito]

Hello, I recently moved to the east SF Bay area in California and have a 1998 Buick LeSabre with out-of-state registration expiring this month (August 2025), and in order to register the car in California I need to get a smog / emissions test.

Can anyone describe exactly what is looked at when taking a car in for a smog test in CA? Search results are giving me mixed information and I'd like to hear from someone who may have done this recently.

I have no idea if they're actually testing for chemical amounts coming off of the exhaust or if they're just looking at computer error codes. The latter is obviously something I could look into at home and see if I can fix it before spending money on the test.

Also, how likely is it to pass a '98 that has 173k miles on the odometer and which probably has the original catalytic converter? Is this something I would need to replace first?

My LeSabre isn't exactly in tip-top shape (clear coat is coming off, couple of surface rust spots, ragtop is starting to look pretty worn, seats have rips), and it's at the point where a bunch of stuff is breaking all at once, so it's not exactly a huge loss, but I'd hate to have to get rid of a perfectly working car just because of this. And now that I'm in the bay area I don't exactly have spare income to purchase another car.

Attached a few of my favorite photos of my LeSabre.

Thanks!

 

[lilpoindexter]

Theres no code scan on '99 and older cars.
They look over your vehicle for any obvious modifications or tampering. Some places slide a mirror under the cat to check the part number against their database of good cat part numbers for your model.
They put the car on rolls and they test at two speeds...they stick a probe in the tailpipe and take samples at two speeds.
Lastly, they take your gas cap off and do a vacuum or pressure test on the fuel system.

On 2000 and newer cars they scan for codes, any codes means you fail, they check readiness monitors, they allow you to not have the readiness monitor for the evap system set and still pass the test.

 

[RD_Atlanta]

A couple of items that might help your readings:
- HC Readings: Change oil soon before going.
- CO Readings: Clean Air Filter & drive at least 7 miles before going (to ensure the engine has reached NOT).
- NOX Readings: Turn on the AC before going, this should force the cooling fans to run (to minimize NOX readings).

 

[DrivenDaily]

From this website regarding how long OBD has been "a thing":

Highlights in OBD history:​

1968 — The first OBD computer system with scanning capability was introduced by Volkswagen.

1978 — Datsun introduced a simple OBD system with limited non-standardized capabilities.

1979 — The Society of Automotive Engineers (SAE) recommends a standardized diagnostic connector and set of diagnostic test signals.

1980 — GM introduced a proprietary interface and protocol capable of providing engine diagnostics through an RS-232 interface or more simply, by flashing the Check Engine Light.

1988 — Standardization of on-board diagnostics came in the late 1980s after the 1988 SAE recommendation that called for a standard connector and set of diagnostics.

1991 — The state of California required all vehicles to have some form of basic on-board diagnostics. This is referred to as OBD I.

1994 — The state of California mandated that all vehicles sold in the state starting in 1996 must have OBD as recommended by SAE — now referred to as OBDII. This stems from the desire to perform across the board emissions testing. OBDII included a series of standardized diagnostic trouble codes (DTCs).

1996 — OBD-II becomes mandatory for all cars manufactured in the United States.

2001 — EOBD (European version of OBD) becomes mandatory for all gasoline vehicles in the European Union (EU).

2003 — EOBD becomes mandatory for all diesel vehicles in the EU.

2008 — Starting in 2008, all vehicles in the US are required to implement OBDII through a Controller Area Network as specified by ISO 15765-4.

That said, 1996 and newer has OBD-2, not the older OBD-1. There should be codes that you can use to help the situation. But if the smog-check techs don't scan during a test, then the codes are there just for you.