2011 Cruze 1.4T P0420 code

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My CEL came on yesterday. Autozone says P0420 code which is the catalytic converter. I have never had a CC go out before. Anyone else have this trouble with the turbo Cruze? I'm curious if there is some other possible cause or if I should plan on replacing CC. Car runs normal temp and has plenty of power so I don't think it's plugged. Drove 140 miles today no issues. Have noticed mpg slowly decreasing for about a year so maybe cat really is fouled due to some other issue like running rich. Hoping someone here has had knowledge to share. Details on car: 2011 Chevy Cruze 1.4 L turbo 160,000 miles (80-90% highway) Uses maybe 8 oz of oil over 6-7k OCI Water pump replaced at 40k & 60k Ignition coil replaced ~10k Turbo oil feed pipe replaced ~120k Thanks in advance
 
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When did you change the spark plugs last? I'd change the plugs if they're close to due and then then the O2 sensors. Cats are expensive. Good luck!
 
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I'm guessing the cat is shot. That engine runs rich during elevated air intake temps while using 87 octane.
 
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Originally Posted By: Leo99
When did you change the spark plugs last? I'd change the plugs if they're close to due and then then the O2 sensors. Cats are expensive. Good luck!
This. With the oil burning and possibly the original plugs, it might be that the upstream oxygen sensor is fouled. A plugged cat would manifest itself first at high RPM, and then at increasingly lower RPM's. OEM iridium plugs are good for 100k miles. If they weren't changed, it's due. The upstream oxygen sensor is right out in the open, so that's likely a fairly easy change too. With a breaker bar, hitting the sensor threads with penetrant while it's hot, and waiting for it to cool. Delco is likely the best bet. Here's a read about the P0420: http://www.easterncatalytic.com/education/tech-tips/the-misleading-nature-of-the-po42o-code/
 

Carbon12

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About the spark plugs, I forgot to include they were changed about 120 or 130k. The old ones had 100k plus and were very clean and not over gapped. If somehow running 87 octane has caused it to run rich, I wonder if correcting any problem(s) and driving a while would burn out some of the soot?
 
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Without looking at the pre & post Airfuel/O2 sensors you're just throwing parts at it. The code only sets if there's a big deviation in the waveforms between the 2 sensors. If the sensor was fouled, you'd get a pumping circuit or slow response code along with a P0420
 
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I bet it's more likely that one of the oxygen sensors has taken a dive. Live data from a scan tool is your friend here. The '11-'16 Cruze 1.4T runs pig-rich from the factory on 87 octane. Mostly to prevent pre-detonation. Nothing like injecting a massive quantity of fuel to cool the hot air from the turbo, since a hotter mixture in the cylinder is more likely to pre-detonate. That extra fuel ends up in the oil and going out the exhaust. Running 93 octane is able to lean out a bit more since 93 octane is more resistant to pre-detonation than 87.
 
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My Toyota FSM indicates O2 sensors should be checked first (assuming tune is done); I did this and my P0420 light was out for probably an additional 50K miles prior to coming on again. I would not be jumping to replace the cat until the "easy" stuff is checked.
 
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Quote:
The code only sets if there's a big deviation in the waveforms between the 2 sensors
Just to be clear, the code only sets if there is NO difference in the waveforms between the 2 sensors. Please read and understand the theory on how ECM determines the catalytic converter efficiency. It is not rocket science.
 
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Originally Posted By: Vikas
Quote:
The code only sets if there's a big deviation in the waveforms between the 2 sensors
Just to be clear, the code only sets if there is NO difference in the waveforms between the 2 sensors. Please read and understand the theory on how ECM determines the catalytic converter efficiency. It is not rocket science.
Agreed.
 
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the code sets if there's a poor mixture being read behind the cat, should always read rich except when coasting... check the rear lambda is working, and for an airleak there... if that's ok, cat's likely toast.
 

Carbon12

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Thanks everyone for the replies. Today I'm going to look for a scan tool. Hopefully I can find one that will read the O2 sensor data.
 
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Originally Posted By: Carbon12
Thanks everyone for the replies. Today I'm going to look for a scan tool. Hopefully I can find one that will read the O2 sensor data.
Harbor Freight's so-called "Professional Scan Tool" does live oxygen sensor data. http://www.harborfreight.com/obd-ii-can-professional-scan-tool-62120.html Their cheaper one doesn't, at least from a quick scan of the description. Good luck, and let us know!
 
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1.4T spark plug interval is 60,000 mi., but as long as they were changed as recently as you said with the proper type it shouldn't be an issue. They do not like 87 octane - many people insist on running premium, but mine gives noticably better performance on 89 so that's what I run. If you want to try to "clean it out" run some top tier premium grade fuel with a bottle of Seafoam or Amsoil PI and make sure you get it on the highway for a continuous 40-50 miles. Also, after running about half the tank, or 2-3 days of the fuel treatment being in there, pull it up hard past 4,000 RPM a few times. The 1.4 has garnered a somewhat bad reputation, but with sensible maintenance and sensible treatment it's a good little mill. Mine has 70K on it. Nothing but synthetic oil since 6K miles, never more than 7,500 mi. OCI, always 89 or 91-93 fuel, and Seafoam every 10,000 mi. No failures or repairs yet.
 

Carbon12

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Update: I bought a nice little Bluetooth code scanner for $22 and the Torque app for $5. Works great with an android tablet. I only had the P0420 code. While trying to figure out what I will do about it I put some Seafoam in the gas. Started using mid grade or premium, ran about a week. I cleared the code and have been running 93 octane all this week in the high heat. CEL hasn't come on since I cleared Monday night. It may come back on or maybe it was just running really rich due to 87 octane in summertime. I'm keeping fingers crossed and plan to run 93 octane or alternate between 93 and 89 every other fill up.
 
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Thanks for the update! Glad to hear it might have been a fluke. Or the engine computer indicating there was an issue with 87 octane in this extraordinarily hot summer we've been having. Might also want to try a bottle of PEA-containing fuel system cleaner like Gumout Regane or Chevron Techron Concentrate (the fuel system cleaner version). PEA is so far the best fuel system cleaner out there.
 
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Originally Posted By: Carbon12
Update: I bought a nice little Bluetooth code scanner for $22 and the Torque app for $5. Works great with an android tablet. I only had the P0420 code. While trying to figure out what I will do about it I put some Seafoam in the gas. Started using mid grade or premium, ran about a week. I cleared the code and have been running 93 octane all this week in the high heat. CEL hasn't come on since I cleared Monday night. It may come back on or maybe it was just running really rich due to 87 octane in summertime. I'm keeping fingers crossed and plan to run 93 octane or alternate between 93 and 89 every other fill up.
Does this app allow you to check the readiness monitors for the catalyst? If so, I would check that information to make sure that the monitors have set.
 
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