Think I may need to replace Catalytic Converter on my 2003 Taco

P0420 is either a leak near the cats or bad cats...I had this code and replaced both cats with Magnaflows and it went away, been gone for 2 years now.

Check for leaks first then tackle the cat if there are no leaks. Be aware though, cheap cats do not last very long. OEM cats are expensive for a reason. Magna flow is a good aftermarket brand that costs considerably less than OEM, but don't expect anything less than OEM to last as long.

 

Well. As I suspected. There are 50 million opinions on this matter and nobody is clear on what is the exact cause. So I gues I will have to let the pros figure it out. Then go from there.

 

Let me be clear.

Your initial mechanic is a crook.

 

hmm.. I might just do this if my cat stops working.. the emissions place where I live only goes tailpipe, CEL and gas cap checks. They don't do a whole big inspection. Would it fail a tailpipe test with this and my cat went bad?

 

What do you mean by that? Initial mechanic?

 

Yep. Tail pipe test will fail with a simulator.

 

Yes, the mechanic that said you need cats just from reading your codes. This completely wrong.

 

Well that wasn't me. Sorry guess you directed that to another poster.

 

@JT1521 3rd pic, check those welds for an air leak, that should be a small heat shield attached on either side. I had mine fall off and they left holes.

4th/5th pic your missing the front CAT heat shield completely, but it's not necessary, only aids in cooling the CAT.

 

Hey OP
The guy who told you that he couldn’t tell what was wrong cause you cleared the code..... he is full of shit, if you came to me, I would be inspecting the hell out of it cause the code is not a definite answer, and I don’t need a code if you can tell me what the code is/was...

 

Yeah that is what I thought too. Anyway did you check my 2 videos showing me checking both Cats with a temp gun? Please do if you didn't and tell me if those temps tell you anything? Thanks.

 

Temps are fairly close, deviation of 100 is not really telling. It IS possible you need the rear cat. If we are just using temps then both need to be done considering both cats should be a lot hotter than your pipe temps.

How old are they? Age degradation is also a reason to swap em.

 

Rear cat does not get injected with air. Not going to be hotter. The extra air the front cat gets will cause it to always be hotter.

Did you ever answer how long the CEL has been lit?

 

CEL has been on for about 6 months. They are both the original Cats. I only have about 108,000 on the truck. Not that that should matter much.

 

Your cats are fine if you can get the truck back in tune. Like 97 said. 500k is nothing for original cats.

 

Age can break down the cat internally, after all there is all sorts of nasty by products in the honeycomb.

 

How would I test the upstream and downstream o2 sensors to rule those out? I have a BAFX Bluetooth OBD2 scanner and use the Torque Pro app but really don't know how to check for bad o2 sensors with it. I also went under the truck and checked for holes and I didn't see any obvious holes.

 

You would need a real scan tool like the snap-on solus one that can do live readings.

 

I tested the downstream o2 sensor after the cat for resistance and it showed 13.5 ohms. Guess that one is fine. Going to test the upstream one tomorrow cause its dark out lol