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Questions tagged [p0420]

An OBD11 fault code for Catalyst System Low Efficiency

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How many catalytic converters does a VW CC 2010 2.0L Sport have?

I have a P0420 code on my VW CC 2010 and I've narrowed it down to a faulty catalytic converter. I have edited this photo to try and explain easier. In the red circle is the catalytic converter I ...
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Would a hole in the catalytic converter cause code p0420?

VW CC 2010. Catalytic converter was replaced when I first got the car at 78k miles. It is now at 83k miles. Downstream oxygen sensor was replaced at 80k miles. There is a small leak in the catalytic ...
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Nagging P0430 (and now a pending P0420 too!) 2004 Lexus ES330

I've got a 2004 ES330 (2nd owner) with roughly 315,000. We didn't pay much for the car in 2012 with 164,000 miles. So, i've never gone overboard in maintenance of it. A year ago, when it was time for ...
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1answer
173 views

Intermittent p0420

I'm working on a customer's 03 Isuzu rodeo with the 3.2 6VD1 another shop had put new catalytic converters and O2 sensors on trying to troubleshoot a bad hesitation problem. I've since fixed the ...
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1answer
478 views

Rear oxygen sensor signal rate of change and p0420

What is the minimum time rate of change (absolute value) of the rear o2 sensor signal voltage that will trigger a p0420 dtc? This is probably vehicle specific, but a ball park figure would help. ...
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1answer
289 views

Should I replace my Catalytic converter?

My 2007 Xterra had the P0420 code pop on. My understanding is that it most likely that the Catalytic converter is going out. If this is the case, how high of a priority is it to fix? Before you ...
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2answers
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07 Nissan Xterra SE catalyst service code

I went to buy an 07 Nissan Xterra SE and it had a Check engine light for a cylinder 1 misfire. So the guy took it to his buddies mechanic shop, and they replaced the one spark plug and coil. Retest ...
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1k views

Can a loose radiator cap cause P0420?

The other day, I loosened my radiator cap and forgot to re-lock it. About 10 mins into my drive home, my CEL came on (and about 2 mins later, I went "DOH!") The code is the always super helpful and ...
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P0420 Catalyst efficiency below threshold bank 1 With CO emission only!

I saw this code in OBD2 scanner on Skoda Fabia 1.2 2006 64hk petrol. It doesn't matter to me except that the car failed the inspection and I'm not allowed to drive it any more. The problem was too ...
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'05 Altima cranks, but will not start (sometimes)

Lately my 2005 Nissan Altima (3.5L) has been reluctant to start, having a 3-5 second delay from the time I turn the key and the starter begins working to the time the engine starts. Earlier today ...
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Affect of burning oil on O2 Sensors

I got a P0420 code and took my car to have a service and an investigate. I was told my car failed an emissions test and that is likely because the O2 sensors have failed causing a rich mix and higher ...
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How could the code point to a faulty cat, when the O2 signals are normal?

I'm getting code P0420 on an '03 Vibe. The rule of thumb is that this means the catalytic converter is gone. Yet the pre- and post- cat O2 signals appear to indicate that the cat is doing its job. ...
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3answers
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my 2011 Chevy Equinox check engine light on, reads code P0420

Check engine light been on. I checked gas cap the other day and it stayed on. I will put premium fuel in next time i fill up. It's been on for about a week. Any ideas to cause or solution?
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Does P0420 on a Vibe result from a pre- or a post- O2 sensor?

My CEL is on and the code reads P0420 on a 2003 Vibe. There are apparently three options: Pre-cat O2 sensor Post-cat O2 sensor CAT model 51274 This is most likely beyond my mechanical abilities (...
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1answer
2k views

Erratic single fault code: P0420, P0440, P0446. Normal variance, or indicative of something deeper?

Working on diagnosing an evap/emission/fuel system problem on my Toyota 2003 Corolla. More on that in this question. On 3/2, I saw a mechanic use his handheld OBD to read a code P0420. On 3/12, ...
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1answer
2k views

1998 Honda Civic - O2 sensor or catalyst failure?

I have the P0420 code on my 1998 Honda Civic DX (catalyst system efficiency below threshold bank 1). I want to be able to properly diagnose the problem myself without just throwing new parts at it. A ...
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3answers
2k views

2003 Toyota Corolla, 185k: erratic OBD codes, fuel smell, other symptoms

TL;DR: O2 sensor data, thermal measurements, and physical resonance tests all point to a failed Catalytic converter. Here's the back story. MIL illuminated with codes P0440, P0420, P0404. Around this ...
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1answer
1k views

Why does the Check Engine code for emissions failure disable traction control and cruise?

I have a 2010 Forester with nearly 100k miles, and it just started giving the "emissions" check engine code (P0420, Catalytic Converter Efficiency Below Threshold). When that code is tripped in the ...
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1answer
119 views

Emissions codes after oil through exhaust

I have a 2003 Subaru Legacy L with the EJ251. I rebuilt the engine because of a thrown rod. There was significant damage to the shortblock, which resulted in a significant amount of oil escaping the ...
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3answers
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P0420 in a Prius

EDIT #2: I rescanned, looking at the correct data, and found the rear O2 sensor was definitely bouncing up and down with the forward sensor's lambda reading. Since I have looked for leaks and couldn'...
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1answer
134 views

Error Codes Related to Transmission?

2002 Ford Mustang V6 My car started having a new problem yesterday. When I drive down the road randomly the pedal loses rpm's. For instance I'll be going 40mph and then there is no resistance on the ...
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06 Chevy Cobalt ls 2.2 l . Replaced B1S1 O2 sensor still having issues

I went and had my 06 Cobalt checked out because the dreeded check engine light came one and I got the P0420 threshold bank 1 code. My mechanic, who has been a good friend of mine for quite some time, ...
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1answer
561 views

P0420 code for 09 Murano

I've had several opinions stating my car needs a cat converter but after failing inspection today, the mechanic said it might need ECT sensor changed. I've read previous posts that cat converters ...
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1answer
773 views

Faulty TCC solenoid or bad computer?

Make: Pontiac Model: Sunfire Year: 2001 Engine: 2.2 L Trans: Automatic Hello to every one, bought my first car and it is fine except for this little annoying problem. After driving it for a ...
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Check Engine code P0420 Catalyst efficiency below threshold bank 1

After months of normal driving with no problems, my 2003 Honda Civic EX check engine light came on during a long trip. Got it scanned and it's P0420: Catalyst efficiency below threshold bank 1. They ...
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What would cause a car to lose power a few seconds after starting, then run normally?

I start my 2003 Honda Civic each morning and drive to work. A few hundred feet down the road, the engine will sometimes behave as though it is running out of gas and lose power momentarily. It doesn'...
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2005 Dodge Ram: Easy way to diagnose code P0420?

My truck is reporting a code P0420, which apparently is "Catalyst System Efficiency Below Threshold (Bank 1)" which can either be the catalytic converter or the rear O2 sensor. The code came on at ...