Trouble Code P0420 Catalyst System Efficiency Below Threshold (1 Viewer)

[Kasprzak]

Just what the title says. I finally got the code read correctly. Any help would be appreciated as I still have not been able to located a reasonably priced service manual. Thanks

Dennis

 

[Gumby]

You have a slow downstream O2, an air leak or a bad cat.

 

[Kasprzak]

Got it..check for leaks...test o2's and hollow out the cats. Simple enough, glad it isn't anything serious

 

[Koffer]

Got it..check for leaks...test o2's and hollow out the cats. Simple enough, glad it isn't anything serious

Its most likely time for the O2s to be replaced . check for leaks also. hollowing out the cats will just set the code all the time as the front and rear o2s will read the same and set the code .
Ive only seen one bad cat. and that was because of a bad set of wires and it was run that way for weeks .
Get OEM o2 and you'll be good for another 80k

 

[4WD Toyota Owner Magazine]

had this in the Cruiser AND a Subaru. Both times, replacing the 02 sensors fixed it!

 

[CJF]

and hollow out the cats

Seems a bit drastic...

 

[Gumby]

I shoulda mentioned that the order of most frequent occurance is the order I listed them, BUT I wouldn't want anybody just throwing $120 O2s at a problem on my suggestion. Gotta at least check for leaks. Then you gotta know it could still be the cat.

Fortunately the most frequent site of a leak on the downstream O2 is at the O2 mounting flange, so when you replace the sensor you fix the problem. it'd be a lot cheaper to replace just the gasket though.

 

[John E Davies]

I replaced my O2 sensors due to this same code about 3 months ago. No more CEL, and the engine runs a little smoother, but it still has a slight miss at idle that has been there since I got the truck 3 years ago. Sigh.

John Davies
Spokane WA

 

[IdahoDoug]

<Hijack>

John,

What do you make of that miss? I've finally accepted that it's a permanent part of the 4.5's landscape. I doubt most would even notice it, but you're in the same sensitivity zone and it bugs me too. Seems vaguely random as I'll notice it one day then not for a month or more. All conditions, all fuels, all ambient temps, all states of tune, etc.

DougM

 

[Gumby]

I have heard a injector tune and balance helps, but you did that, didn't you, Doug?

I got mine to go away while Lucas FI cleaning was in, but it came back as soon as I ran out of treated fuel.

I have driven one that didn't do it.

 

[ryanjl]

SEARCH for P0420. There are a few threads on the code, some VERY in depth.