It is not the O2 V readings that set it off. It is the test that gets run sometime after the EVAP runs, sometimes before. The best mine has done is about 1000 miles after the EVAP, the worst about 200 miles after reset.

Trust me, I have been trying to believe the cat is not bad for 9 months now. I have my laptop setup in the car constantly monitoring the O2 sensors. I have used Google for hours finding out about the OBDII testing.

The test it does is basically: after warm up at idle it commands the injectors rich momentarily and checks how fast the #2 sensor reacts (the test is triggered by some magic AlGoreithm). There is a bit more to it, but you can do Google just as well as I can.

The code being absent only means the test has not run, not that it is good.

Sorry, you are doomed to a new California rated cat! I spent lots of time and money for you.

 

The temp test was just a back yard type of test.(a place to start) the only way to truly test the convertor is with a four gas analyzer and a tech that knows how to read it.

Converters convert HC into CO2 and by reading the CO2 numbers with different tests the tech can see if the convertor is good,weak,or not working at all.

 

I checked this afternoon with a local Chevy dealer and the parts man said the estimated cost of a dealer/CARB approved cat is around $825 plus a core charge. I said I can replace it which he said was fine. I checked at Magnaflow and Walker both have CARB approved universal fir cats and are around $300. When my wife's 2003 Deville needed a cat earlier in the year the shop installed a Magnaflow cat and it passed smog just fine and we did install new O2 sensors at the same time so it took several days for the self tests to run and clear everything off.

Has anyone tried one of the universal cats on their HHR and I realize that it means cutting the pipes on both sides of the stock cat and I have an exhaust pipe cutter so that is no issue. I imagine the universal cat comes with the letter like the one for our Caddy did with the CARB number, etc.

 

One of the shops I do business with does that all the time. In fact, at least in VA if you have one that has the second cat (like my 2011) they gut the second one, since the O2 sensor only monitors the first one. He told me "nobody sticks a sniffer up the tailpipe anymore".

I have no idea what the whacko tree huggers in CA have made into law.

 

I got my new cat in the mail today and installed it, need 11 more cold starts to know for sure.

The #2 O2 sensor now gives a dead straight reading even when cruising (not when accelerating). Right about .790V just as before, but dead straight graph.

I think it needs some breaking in because for a time it was reading .600V dead straight after a warm up period. It didn't occur to me to monitor the temperature .

 

Soooooo, what cat did you install finally and where did you get it please?

 

I do not live in California, where I live in Virginia I don't even need emissions testing.

I got mine on Ebay from a Canadian vendor for $189 shipped, the 2011 models have 2 cats on the pipe so they cost more. Clearly stated "not legal for sale in California, not legal for use on cars registered in California".

You need to check the tree hugger laws, I seem to remember the word "felony" being involved.

 

I talked with the mechanic that does some work on our cars from time to time and he said the CARB approved universal cats are okay to use but you have to cut the pipes which he said is a pain.

I was curious if the cats sold by GM Parts Direct: Your direct source for Genuine GM Parts are CARB approved as their website notes they are "genuine GM parts and the parts man I talked to the other day said only one model cat was listed for the 2007 automatics? A different one was listed for the 2007 manual trans cars?

 

You would need to talk to a California smog control expert. Although I was born there, I don't qualify.

 

Well it has been several weeks since I replaced the #2 O2 sensor with a new one and so far the on board diagnostics have all completed and there have been no codes. I ran the AutoEnginuity data logger several times with the #1 and #2 O2 sensors voltage recording and as it should be, #1 jumps around, especially when I hit the gas hard. #2 O2 sensor stays steady as a rock all the time, no dips or blips which tells me the CAT is fine. So my Porsche mechanic friend who said to replace them at 60K miles, especially if you have to live with gas like we have in CA with all those anti-smog chemicals seems to be true! RockAuto.com ships them from central CA so I only paid a few $$$ for shipping and got it in 2 days!