P0420 Code After a New Fuel Injector! Please Help!

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Hello guys! My 2003 Vibe base model AWD had codes P0301 (Cylinder 1 One Misfire Detected) and P0420 (Catalyst System Efficiency below Threshold (Bank 1)) when I bought it. I changed the fuel injector and the P0301 engine code went away. Unfortunately, the P0420 engine code did not go away. I tried erasing the code and driving my Vibe for a while. I wanted to see if P0420 code was a code related to the P0301. Nothing has changed. As of now, when I drive my Vibe for about 15 minutes the light comes as P0420P. P0420P means as you know that there is a pending P0420 and that the CEL will come on in any moment. I was thinking about bad O2 sensors because the Vibe drives fine even with the P0420 CEL on. When there is a bad catalytic converter, the vehicle usually does not run smooth or it feels with no power. But I let the Vibe parked for a while and when I started it, the Vibe had a very bad smell coming from the exhaust. The smell was not gas related but like rare gases. Now, I am confused. I have read a lot online and many people suggest changing the oxygen sensors before changing the catalytic. WHAT YOU GUYS THINK!! Your suggestions will be greatly appreciated! Thanks!

Updates 10/29/2012: I removed the exhaust as well as the rear O2 sensor. The sensor was kind of dirty and I cleaned with brake cleaner. As far as the CAT, I tried something that heard about cleaning it with Lacquer Thinner. I used a full gallon on the CAT, but it did not help. After putting everything back together and running my Vibe for a while, I scanned the Vibe for CEL codes and I was still getting a pending P0420P. After driving for more time, the CEL came back on.





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Another thing, one mechanic also told me that when the catalytic converter goes bad in a car, the P0420 could take even a week or two to show up. In the other hand, when the P0420 is showing due to a sensor, the CEL shows right away (one or two days). What do you thing about this?

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Anybody?

[Salsa Guy]

Having that code normally means a bad CAT or less likely a bad O2 sensor (located after the CAT). Having a plugged CAT will cause the car to run badly but having a CAT not work well doesn't mean it's plugged. You can try a defouler ($10 part) on the rear O2 sensor and see if it clears it. If not you'll need to replace the CAT.

[Reaccion]

Having that code normally means a bad CAT or less likely a bad O2 sensor (located after the CAT). Having a plugged CAT will cause the car to run badly but having a CAT not work well doesn't mean it's plugged. You can try a defouler ($10 part) on the rear O2 sensor and see if it clears it. If not you'll need to replace the CAT.

Okay, thank you for replying Salsa Guy. I thought that if the catalytic was bad, it could feel plugged. I am going to try the defouler with a new rear
O2 sensor and see what happens. Do you have an idea where to get a CAT in a good price? A mechanic told me not to go aftermarket. He pointed that the aftermarket CATs are very cheap and would probably trigged the code again.

[Salsa Guy]

I wouldn't replace the rear O2 just yet. You may even consider replace the front O2 because that controls how much fuel you are putting into the engine (along with the MAF) and if it's too much it will (removed) the CAT.

[Reaccion]

I wouldn't replace the rear O2 just yet. You may even consider replace the front O2 because that controls how much fuel you are putting into the engine (along with the MAF) and if it's too much it will (removed) the CAT.

Okay. This means that you are suggesting replacing the front and rear O2 sensors. It makes sense.

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I find it crazy that the check engine light comes on even with a 20 minutes drive.

[Salsa Guy]

Do the defouler first! Chances are the CAT is bad but the defouler will buy you time. If you start losing power and MPGs go down it's time to replace the CAT. The rear O2 isn't exposed the extremes of temp as the front. There has been some posts about the Front O2 causing the engine to run rich and fouling the CAT.

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Do the defouler first! Chances are the CAT is bad but the defouler will buy you time. If you start losing power and MPGs go down it's time to replace the CAT. The rear O2 isn't exposed the extremes of temp as the front. There has been some posts about the Front O2 causing the engine to run rich and fouling the CAT.

Yes, I understand. I would not be able to compare the MPG because I just got this vehicle with this problem. I would not know the MPG with or without a good CAT. Sometimes, there is a very rare smell like gas or something that I would not be able to explain it.

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Anybody has ever install an aftermarket CAT? If so, which brand and how does it work?

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This is so confusing. After driving even for 10 minutes and having the CEL reset, I have a CEL rescan and I P0420P. To my understanding this code is a pending P0420. The Vibe practically shows this P0420P code right away. After certain amount of miles t is when I get the P0420 code accompanied by the P0420P as well. Any other ideas based on this?

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I noticed that the rear muffler tip is very, very smoke dirty in the inside. So, if the catalytic and sensors are as dirty as the exhaust tip, all components inside the exhaust should be clogged and dirty.

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Updates 10/29/2012: I removed the exhaust as well as the rear O2 sensor. The sensor was kind of dirty and I cleaned with brake cleaner. As far as the CAT, I tried something that heard about cleaning it with Lacquer Thinner. I used a full gallon on the CAT, but it did not help. After putting everything back together and running my Vibe for a while, I scanned the Vibe for CEL codes and I was still getting a pending P0420P. After driving for more time, the CEL came back on.

[Salsa Guy]

Did you ever try the defouler on the O2?

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Did you ever try the defouler on the O2?

No, I have not try the defouler yet. what are the specs and where could I find it?

[star_deceiver]

A defouler is simply a piece of pipe that takes the 2nd O2 sensor out of the exhaust stream. You'd have to make one yourself, piece of pipe threaded to accept the O2 sensor and then threaded/welded into the exhaust pipe. I suppose you might find one online.

[Reaccion]

A defouler is simply a piece of pipe that takes the 2nd O2 sensor out of the exhaust stream. You'd have to make one yourself, piece of pipe threaded to accept the O2 sensor and then threaded/welded into the exhaust pipe. I suppose you might find one online.

Yes, Thank you for your comment. I was looking for one online and this is very cheap. I am trying the defouler before jumping on an expensive CAT. This might buy me some time until I coult change the CAT.

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[Salsa Guy]

They may have them at your local Auto Parts store. Normally they have the same threads as spark plugs and some times used for spark plug defoulers. We used them on a old car that bad rings to keep the Spark Plug from getting crapped out.

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They may have them at your local Auto Parts store. Normally they have the same threads as spark plugs and some times used for spark plug defoulers. We used them on a old car that bad rings to keep the Spark Plug from getting crapped out.

Very nice, that is a great idea. I actually already ordered one online for only $10.95 (Shipping included). Let's see how would it work! I will keep you guys posted!

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I am going to install the defouler. If the CEL does not come back, I would know for sure that I need to replace the CAT.

[Salsa Guy]

You spent way too much time and effort trying to cure your CAT issues. The P0420 is a sign of a bad CAT or less likely a bad O2 sensor (after CAT) and even maybe a bad O2 in the Manifold. The Defouler will only mask the issue. Hopefully your CAT will not plug then cause some really bad things.

Goodluck

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You spent way too much time and effort trying to cure your CAT issues. The P0420 is a sign of a bad CAT or less likely a bad O2 sensor (after CAT) and even maybe a bad O2 in the Manifold. The Defouler will only mask the issue. Hopefully your CAT will not plug then cause some really bad things.

Goodluck

I know man, and you are 100% right. I am just trying to troubleshoot it using the defouler. I am going to install the defouler to test the Catalytic. If the CEL does not come back, I would know for sure that I need to replace the CAT. In the other hand if the light comes back on even with the defouler, then I would know that the CAT sensor is not good.

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The defouler worked. The CEL went off. Even the OBD2 scanner says that the car is ready for inspection. This is great, I know now that the problem is really the CAT and not the sensor. I am now ready to change the Catalytic to be ready for inspection!