Still Have P0420 - 2000 Soloa SE - Replaced A/F, Rear O2 & Cat

[boofertjustice]

My girlfriends 2000 Solora SE (CA) has had the P0420 problem for some time now. Here's what I've done so far...

1) Scanned, got P0420
2) Replaced front A/F sensor
3) Reset CEL, drove, CEL came back, scanned, got P0420
4) Replaced rear O2 sensor
5) Reset CEL, drove, CEL came back, scanned, got P0420
6) Replaced cat
7) Reset CEL, drove, CEL came back, scanned, got P0420

I'm kinda at a loss of what to do next.

[hill8570]

Originally Posted by JJJJJJ

None of what you did is 04020 related, you put a lot of money into it already - it's carbon buildup or VSV modulator.

In this order:

clean/replace Vaccum lines
check EGR modulator and EGR valve for vaccum
clean EGR valve
replace EGR VSV modulator

OK, are we talking about a P0402 (which points to an EGR flow issue, as J^6 points out), or P0420 (cat efficiency below threshold), which seems to be what boofer is trying to troubleshoot?

[hill8570]

Ass-u-ming that we're talking a P0420, have you checked the exhaust system between the exhaust manifold and the rear 02 sensor for any holes or leaks?

[boofertjustice]

Originally Posted by hill8570

OK, are we talking about a P0402 (which points to an EGR flow issue, as J^6 points out), or P0420 (cat efficiency below threshold), which seems to be what boofer is trying to troubleshoot?

Hill is correct, the P0420 (cat efficiency below threshold). As I wrote and double checked twice before posting. Please read carefully.

Originally Posted by JJJJJJ

Read it as an EGR issue - maybe it's a cat issue.

I said I replaced the cat. Please read carefully.

Originally Posted by JJJJJJ

Did you use Bosch, NGK/Denso, or other for the 02 sensors ?

Bosch sensors, A/F & O2.

Originally Posted by JJJJJJ

Do you have CA emission ?

CA with A/F sensor, as I mentioned. Please read carefully.

Originally Posted by JJJJJJ

What model of cat did you install ?

A metal with some stuff inside to burn off excess gas. No brand name.
The sensors were tested via ODBII and seemed to be within their respective ranges.

Originally Posted by hill8570

have you checked the exhaust system between the exhaust manifold and the rear 02 sensor for any holes or leaks?

No.