I received the P0420 code on my 04 TSX about 8 months ago with roughly 148,000 miles on it. I tried the seafoam trick and premium fuel but the light keeps coming back on. I have an emissions test coming up in roughly 3 weeks and I just want a cheap solution to pass emissions. Any ideas? Should I replace the 02 sensors first or the CAT? I know the OEM sensors and CAT are expensive. Would the aftermarket products work to get me through emissions?
Any help is greatly appreciated!

 

2004 P0420 is unrelated to O2 sensors UNLESS a sensor error code is sent at the same time. The only trouble shooting you can do is several tanks of top tier premium fuel with maximum allowable fuel system cleaner additive, such as techron, and hope the issue ISN'T the cat.

Step 9 in the process is replacing your cat.

There is no cheap solution. If, as I read between the lines, you've been running generic regular gas for 140k+ miles, I think the chickens have come home to roost. The use of sub-optimum fuel (regular) can result in a slow build-up of contaminants in the cat honeycomb. This slowly plugs the cat and eventually throws an error code as performance deteriorates below required levels.

Sea Foam only addresses intake and cylinder issues, thus you wasted your money and time there.

If it's the cat, the only prayer you might have is good fuel and a code clearing just before you go to the test (just = right down the street, if you can) and hope you're in right with The Man.

 

Interesting post (and addressed to who it should be. The cheap f*cks who think they can buy a relatively high performance and technologically sophisticated car like the TSX and then treat it and maintain it like it's a 71 Chevy (Regular gas? Give me a break!!). Expensive things often have expensive problems. And for anyone who might think that getting the emissions controls on a TSX up to snuff is expensive, try a $5000 "15K mile service" for a Ferrari. Seafoam won't help you there....... Gees!!

 

PO420 is the infamous cat code... like DuckDodgers said have the code cleared. it may or may not come back. Emissions systems are two trip so the problem would have to be detected by the computer two times before the light comes on. I have seen these go either way but I would start saving even if you get it to pass inspection because a new cat is most likely going to be needed.

 

The code has been cleared multiple times and it keeps coming back. Does anyone know if this CAT would do the trick?

http://www.autopartswarehouse.com/de...7.html#reviews

And this for an O2 sensor?

http://cgi.ebay.com/ebaymotors/Accor...item2c5c0c10c1

 

Again, why the O2 sensor concern...no code and you can continue to use current.

 

Run the vehicle thru the emissions test and report back with the results. No sense throwing parts at it until you know what the problem is. But, my money is on a dead cat.

 

a dead cat results from low grade fuel, pls pls 98+octane petrol only

 

imo dont throw your money away on an aftermarket cat. you'll still have the code. to answer your original question as far as a cheap and simple solution google "spark plug defouler p0420" its basically a drilled out spark plug defouler that serves as a spacer. the spacer fools the secondary o2 sensor into thinking the air running thru it is cleaner than it is. I have no idea if this would work on a tsx bc i have only worked on 90's hondas. only real way to fix this problem youre describing is a new oem honda cat....

 

The anti-fouler spacer will probably work, but no way to know but try.

I used this kludge to fix a Subaru Forester w/ P0420. Foresters are notorius for this code, but Acuras don't seem to suffer this fault very frequently (experience w/ TL's not TSX), so a new converter is probably long term fix.

I tried an Eastern converter on my Forester and it worked for 1-2 yrs, then code returned, whence I went w/ kludge. It was permanent fix.

good luck

 

No, that wasn't a permanent fix. The only permanent fix is to replace the cat(s)

These fixes just cover up the problem to pass a test, but the dirty air is still spewing out of your tailpipe.

 

Here is a video on YouTube for a P0420 fix. The car is a TSX in the video too. It might be worth a shot.

http://www.youtube.com/watch?v=5icTmYItwiE