P0420
01-28-2019, 02:59 PM
#1
P0420
I need some help with a P0420. I don't know if anyone can shed some light and point me in the right direction. I've been having intermittent P0430/P0420 codes ever since 2013. I have stock cats with a Bassani cat back exhaust. The car always throws a P0A00/P0A03 code initially then disappears and throws the catalytic converter codes. At first it was Bank 2 having a problem throwing a P0A03 then a P0430. I had a hard impact with a rock on the drivers side cat so I figured that's why it was bad. I put in a used cat with 40k miles, new oem downstream sensor and the code hasn't comeback in almost 2 years. Now, I having issues with Bank 1. It threw a P0A00 right before my smog check in 2017. I didn't want to diagnose the problem and just put another used cat with 40k miles on it, new oem downstream sensor. The code went away for 5 months then came back as a P0420 code that would show up every couple months after I cleared it. I know my cat is probably bad now from whatever is going on.
I have the freeze data of when the SES light was triggered with engine RPM, short&long term fuel trim. I looked at my o2 sensor data on a scanner and they seem to be functioning correctly. I have new OEM upstream o2 sensors but my mechanic claims the original ones are rusted on the headers and wants to charge a rediculous price to install the new ones. I don't want to change them out yet unless its really necessary.
6/17/17 P2A00 1262 rpm S:0.00% L:2.34%
11/11/17 P0420 2388 rpm S:0.00% L:2.34%
5/14/18 P0420 2425 rpm S:2.34% L:2.34%
12/12/18 P0420 2562 rpm S:6.25% L:2.34%
1/27/19 P0420 2138 rpm S:-1.56% L:6.25%
I remember that a week before I got the P2A00 code I took off my JWT dual intake and put the stock airboxes back in. The other day I noticed my passenger side intake hose has 3 small hairline cracks in it. One at each end by the clamps and one by the noise reducer box. The cracks don't all the way through the hose to the inner diameter. The driver side also has 1 tiny crack by the airbox clamp and isn't nearly as bad as the passenger side. Would there be a chance this is causing the problem? The only other things I can think of that could be wrong is the MAF sensors, fuel injector, air leak in the header/cat/plenum. I'm not a mechanic and not really sure where to start to diagnose the problem. I've seen plenty of threads about P0A00/P0A03, P0420/P0430 problems but people don't really post the solution.
I have the freeze data of when the SES light was triggered with engine RPM, short&long term fuel trim. I looked at my o2 sensor data on a scanner and they seem to be functioning correctly. I have new OEM upstream o2 sensors but my mechanic claims the original ones are rusted on the headers and wants to charge a rediculous price to install the new ones. I don't want to change them out yet unless its really necessary.
6/17/17 P2A00 1262 rpm S:0.00% L:2.34%
11/11/17 P0420 2388 rpm S:0.00% L:2.34%
5/14/18 P0420 2425 rpm S:2.34% L:2.34%
12/12/18 P0420 2562 rpm S:6.25% L:2.34%
1/27/19 P0420 2138 rpm S:-1.56% L:6.25%
I remember that a week before I got the P2A00 code I took off my JWT dual intake and put the stock airboxes back in. The other day I noticed my passenger side intake hose has 3 small hairline cracks in it. One at each end by the clamps and one by the noise reducer box. The cracks don't all the way through the hose to the inner diameter. The driver side also has 1 tiny crack by the airbox clamp and isn't nearly as bad as the passenger side. Would there be a chance this is causing the problem? The only other things I can think of that could be wrong is the MAF sensors, fuel injector, air leak in the header/cat/plenum. I'm not a mechanic and not really sure where to start to diagnose the problem. I've seen plenty of threads about P0A00/P0A03, P0420/P0430 problems but people don't really post the solution.
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sbZenth
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07-16-2008 08:28 AM