P0420 code...again

[slowdime]

I replaced the catalytic converter in my S10 a little over 2 years ago. I checked and there were no oil or coolant leaks to dirty up the catalyst and it hadn't melted from fuel entering the exhaust. I replaced it with a magnaflow cat even though I strongly prefer OE, I was unemployed at the time and needed to re-register the thing in short order.
I had a P0420(catalyst below efficiency) code come up about 6 weeks ago, I cleared the code and it hasn't returned....yet
What do you all think about replacing the oxygen sensors before buying another cat? If it truly isn't doing it's job one would think the code would have been thrown again at some point in the last 6 weeks, but it hasn't. The o2 sensors are the ones GM installed in the factory so they've been in there for about 12 years and 140k miles, not exactly spring chickens...
Any o2 sensor recommendations? AC Delco or Delphi would be my first choice as they are oem equipment but I work part time and I'm also back in college so my budget is pretty tight. I can get Bosch for both the upstream and downstream and only be out $47. Are Bosch's o2 sensor better than their spark plugs?

 

[dparm]

Remove the sensors and clean them with electronics cleaner. Inspect the wires and harnesses for damage. Also, bang your fist on the cat converter and listen for rattling (indicating a broken catalyst brick).


I'd get whichever O2 sensor is cheaper. NTK, Bosch, etc are all fine.

 

[ARB1977]

Change the sensor and run a O2 simulator to keep the light off. That way the computer is tricked in thinking everything is fine.

 

[FL_Rob]

Originally Posted By: ARB1977
Change the sensor and run a O2 simulator to keep the light off. That way the computer is tricked in thinking everything is fine.



Would you recommend O2simmulator.com ...or similar site, or is there a specific brand that really works well?

 

[tommygunn]

Walker and Eastern cats are much better. I think Walker might actually be the OEM supplier for your S10. I know that they do a lot of OEM cats.

It's usually a good idea to replace the upstream sensors when you replace the cat.

 

[dparm]

Magnaflow/Carsound sells a lot of direct-fit OEM cat replacements. Most exhaust shops can get them for you.

 

[sw99]

If it were me, I would totally try a gallon of lacquer thinner. Some say it works and some say it doesn't... Worth a try for $12 and some driving.

 

[GMBoy]

Originally Posted By: ARB1977
Change the sensor and run a O2 simulator to keep the light off. That way the computer is tricked in thinking everything is fine.


Cheaper way....poison the after cat sensor with RTV silicone. It will then be steady and fool the computer into thinking the cat is efficient.

Not the best or legal way, but will turn off the light until you fix it right.

 

[artificialist]

Sometimes the ACDelco or Delphi sensor is really an NTK brand sensor, or a Denso sensor. Read the existing sensors on your truck carefully, and you may find NTK or Denso markings. Then see if the equivalent sensor is cheaper.

I have replaced NTK with Denso and replaced Denso with NTK and had no problem.

I have heard mixed reviews of Bosch O2 sensors used where Bosch was not OE.

 

[FL_Rob]

Originally Posted By: GMBoy
Originally Posted By: ARB1977
Change the sensor and run a O2 simulator to keep the light off. That way the computer is tricked in thinking everything is fine.


Cheaper way....poison the after cat sensor with RTV silicone. It will then be steady and fool the computer into thinking the cat is efficient.

Not the best or legal way, but will turn off the light until you fix it right.



What,you just take it out and goop up the sniffer end and replace it?...or..

 

[zzyzzx]

I use Bosch O2 sensors on everything (except Toyotas) and they work great. I even have one with ~145K miles on it and it still works fine (being defined as no dash light and OK MPG).

If you need to try an O2 spacer.

 

[shinyWheels]

Try take a look at this video. It was pretty helpful in helping my friend diagnose his P0420 code.

http://www.youtube.com/watch?v=9VZ5K8n5jj0

 

[Warstud]

Maybe the blower quit working.

 

[artificialist]

Originally Posted By: Warstud
Maybe the blower quit working.

Blower? Meaning Secondary Air Injection?
OBDII cars check the air pump to determine if it is functioning. He would get a "Secondary Air Injection" error code, I forgot which number that would be.

 

[PandaBear]

Can you try a washer / spark plug non fouler? I'd use those over any simulator.

 

[ram_man]

the magnaflow cat is probably the issue. in my experience they have been absolute junk. that cat should still be under warranty to. if it is utilize it.