lexicdys???? Don’t think osMy post shows the graph with H2O in mV and both O2 sensors working. Maybe the H2O sensor measures the water in my wiper fluid…or rainfall….o

 

From having worked with pressure sensors as an engineer, I was skeptical that the sensor would go bad without setting the other sensor problem codes (stuck high or stuck low). This sensor application is not a high-precision application in which a small drift in output would be critical.

According to the manual, the P0451 code can be set by a bad sensor, blocked vent line (unlikely as the line is pretty big diameter), or a plugged EVAP canister.

Earlier this year the car had a code which implicated the vent solenoid. I bought a new solenoid and noticed that the old one had some powder residue in it. The new solenoid worked and everything was fine.

A couple of days ago, I swapped the EVAP canister from my 2009 HHR with my son's (the one having the issue). When I removed the EVAP canister from my son's car and tapped the canister onto the table, some debris came out of the tube that connects to the vent line. It's a 5 minute job to remove and replace the EVAP canister, one 10mm bolt and a bunch of quick-disconnects.

With the swapped EVAP canister, no more P0451 code. The canister was bad. Interestingly, the bad canister hasn't set a P0451 code on my car (yet). Maybe shaking the debris out cleared it? Anyways, I am ordering a new canister from Rock Auto ($100) to replace the bad one installed on my car.

We have been driving the car for the last few days waiting for either the catalyst test or EVAP test to run so we can get the car inspected.

Steve

 

Is the canister specific to the SS or would one of your parts cars canister work?
I looked up a 2007 2.2 ( Oldblue)
and a 2009 SS , your son’s and , we’ll have a look, they are the same part number

 

When I changed my vent valve I was amazed at the amout of dust that voluntarily fell out. I suspect that is the cause of many EVAP codes.

 

Even though I fixed the P0451 code, the Catalyst and Evap tests would still not run.

I checked the conditions under which the tests would run in the Service Manual. There were a bunch of them that I monitored with my bluetooth scan tool and it appeared that they were met.

I removed the tuned PCM and installed the original PCM (along with the original 2-bar sensors) and the catalyst test ran quickly after a short time of driving. Looks like the tune must change some parameter which inhibits the test.

Steve

 

Some tunes turn the #2 O2 sensor off, for removing the cat. There might be an option to turn it back on.

 

That's definitely a possibility. I'll talk to the tuner (ZZP) and see what they say.

Steve

 

Strange they turn off the second O2 sensor, when it’s in the pipe before the second catalytic converter . Just a note, hellshotrod has a down pipe available

 

The #2 sensor is the one that senses the health/existance of the cat. The second cat is basically redundant, it scrubs the already scrubbed exhaust gas (for California and New York).

 

Yes, but why turn off the second O2 sensor? It senses the exhaust after the first catalytic converter.