Read up on New Jersey and California.

 

GM follows the government guidelines for emissions, for all states and the countries the HHR was exported to.
A catalytic failure can be a result of a coolant leak or oil consumption . Or can be even from the wrong spark plugs.

 

I'll keep my fingers crossed that eventually it will pass. I don't see any oil leaks luckily.

 

SE WI has been doing emissions testing for over 30 years. It was a pain before OBII came long. They used a wand to collect exhaust gas and issue a pass/fail. Then it was a crap shoot as to why it failed.

OBDII made this all really easy to diagnose. I have driven all GM cars and have never had issues getting one to pass. So long as there are no codes, no pending codes, nor any readiness state issues. The rule of thumb has always been if the computer is reset, or a code is cleared, put 100 miles or more on it before testing.

A cat can also fail from having a bad thermostat. Running a little too cold can cause the computer to run the system rich and eventually melt the inside of the cat. Had this happen on my old Trailblazer. Actually it's a common issue on Trailblazers. No fun towing a travel trailer on the Interstate with a crippled exhaust.

 

Hey Doc thank you for replying. I hope my cat is not melted🤤. The car seems to run good, I am gonna take it on a small road trip this weekend and see if this helps

 

A melted catalytic converter would set a code like P0420.
I suggest drive it and allow the tests to run as Donbrew posted.

 

It would take a lot of heat to melt the core of a converter. The thing would have to glow cherry red and there would be a smell and no power.
Many times on the trucks I worked on with Caterpillar engines in them there was an ash burn test for the converter.
This would raise the inlet temperature much higher than normal operation. And that didn't melt the core.
Those converters measured in and out temps and pressure. Granted this was for a diesel engine that can produce soot in the exhaust versus a gas engine.

Here's something to read:
https://www.obd-codes.com/p0420

 

Not necessarily. You'd think so of course. Trailblazers with 4.2 I6s (not the 5.3s) were noted for CAT failures which often tied back to bad thermostats, which then caused the computer to run it rich. No codes. Not even pending codes. Just a noticeable loss of power. Now granted HHRs aren't noted for failed CATs but it's something to consider.

I suspect it's very different for a diesel. I didn't even know they had cats. As said above, very common issue on 4.2 I6s. Never got hot enough to notice anything. It was very gradual. No codes. And ran just fine under normal operating conditions. If it was under load, like hard acceleration from a dead stop or towing a trailer, that it simply had no power. That's the only way people would know something was wrong.

 

Hey Doc:) thank you for responding! Currently, there is one monitor that still not ready and that monitor is the EVAP. The other remaining monitors are claiming to be ready. I plan on to sign it to be inspected this week so fingers crossed🤞

 

That's awesome. How many miles have you had to put on it to cycle through everything?