An OBD11 fault code for Catalyst System Low Efficiency

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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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2answers
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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
89 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, ...
4
votes
1answer
66 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 ...
7
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3answers
378 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 ...
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1answer
97 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 ...
2
votes
1answer
76 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
3k views

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'...
2
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1answer
81 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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3answers
6k views

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
217 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 ...
2
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1answer
530 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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3answers
69k views

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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3answers
34k views

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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2answers
13k views

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 ...