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Discussion Starter #1 (Edited)
My 2014 Cruze with 1.4 is running fine but we had a engine light and there’s a P0420 code. Hesitate to mess with plugs given the trouble people have with plug boots tearing. Is there a way to figure out if it’s the plugs, 02 sensor or ??? I am going to replace air filter. I disconnected the battery to check a couple things like 02 harness and now no engine light after reconnecting battery so far, but it’ll probable come back on. Anyone else deal with a 0420 code?
 

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Welcome Aboard!:welcome:

I am moving this thread to the Gen1 Service Issues.

In your case, the P0420 code stands for “Catalyst System Efficiency Below Threshold (Bank 1).” When you receive aP0420 code it means your catalytic converter is not operating at maximum efficiency. Usually this means your catalytic converter needs to be replaced or there is a problem with your O2 (oxygen) sensors.
For more info go here








































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Don't forget to introduce yourself and your Cruze here.
 

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I'm having the same problem with my '14 ECO. Ive just replaced both o2 sensors so far with no help, I justified it because its creeping up on 100k and I figured its about time to replace anyway. Next up will be spark plugs for me. If it rolls over 100k with the 0420 code still, I'll do a catless downpipe and retune the computer to ignore the downstream o2.
 

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Hi Richlo1, did you figured out what was the cause. Mine it's 2014 as well, I already changed both O2 sensors, catalytic without luck. I don't want keep spending a fortune with this issue. The engine doesn't behave different than before to this issue.
 

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Hi @Blasirl, thank you to take the time to answer me.
I have been struggling with this issue for the last 3 weeks. My mechanic has already looked for spark timing, exhaust leak, bad injectors. We already removed the exhaust pipe but no luck. Engine light always comes on with same code after few cycles of driving, usually 2 or 3.

Have you reset the codes and re-polled the car yet?
 

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I have not gotten mine to go away either. For me just both o2 sensors, new spark plugs and fresh amsoil so far. And yes I cleared the code after every change to see if it would stay off and it doesn't. Same thing after 2-5 driving cycles it'll turn on. The weird thing is that when it first started it would sometimes turn itself off for a couple cycles then turn back on.

Just curious, what gas are you running? I have not tried ethanol free 91 yet but I might try. I usually fill up with 15% 88 octane b/c its cheaper than 10% 87.
 

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Weird update for me, I hopped in this morning to go to work and the light was turned off and it stayed off for the whole drive in (about 1 hr). I didn't change anything, the only thing is that it was around 30 degrees F outside, if that has any effect on it?
 

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I'm having the same problem with my '14 ECO. Ive just replaced both o2 sensors so far with no help, I justified it because its creeping up on 100k and I figured its about time to replace anyway. Next up will be spark plugs for me. If it rolls over 100k with the 0420 code still, I'll do a catless downpipe and retune the computer to ignore the downstream o2.
Hey Rich,

My cruze has same mileage yours did when code went on. I know you did a number of things like 02 sensors and plugs and such. Did you ever get to the bottom of it? Thanks. Hope you can save a guy some trouble...
 

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Hey Rich,

My cruze has same mileage yours did when code went on. I know you did a number of things like 02 sensors and plugs and such. Did you ever get to the bottom of it? Thanks. Hope you can save a guy some trouble...

So I replaced the spark plugs last and it turned itself off shortly after replacing the spark plugs and it went away for about 7k miles and now its back again. That is the longest it has gone away since it started throwing that code. So I'm inclined to replace the coils next? I'll be shopping around for a better setup though, I have already had problems with the coil which was covered under warranty but now that its over 100k I'll be looking for an aftermarket upgrade. Either way I'll post updates here if I find a cure or not.
 

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So I replaced the spark plugs last and it turned itself off shortly after replacing the spark plugs and it went away for about 7k miles and now its back again. That is the longest it has gone away since it started throwing that code. So I'm inclined to replace the coils next? I'll be shopping around for a better setup though, I have already had problems with the coil which was covered under warranty but now that its over 100k I'll be looking for an aftermarket upgrade. Either way I'll post updates here if I find a cure or not.
Do you have an update on your car? I have a recurring P0420, both the O2 sensors an the CAT were replaced. Still no McLovin'.
 

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No, just getting through winter, I still have the code and It still turns itself off once in a while for a short period of time before coming back on.

Come spring or summer I am going to get this upgraded coil kit to try out.
BNR LS7 Coil Upgrade LUV-LUJ 1.4T

If somebody else wants to try it first you could possibly save me $600 :eek:ccasion14:
 

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So I replaced the spark plugs last and it turned itself off shortly after replacing the spark plugs and it went away for about 7k miles and now its back again. That is the longest it has gone away since it started throwing that code. So I'm inclined to replace the coils next? I'll be shopping around for a better setup though, I have already had problems with the coil which was covered under warranty but now that its over 100k I'll be looking for an aftermarket upgrade. Either way I'll post updates here if I find a cure or not.
Thanks for the update. Ignore private message, where I asked you if you replaced plugs yet...

I am going ahead and replacing my spark plugs. Anyone have a brand preference? OEM always for me, but I would take a reference from someone who has had good results from trying something other than OEM. My Ex-brother in law would say as a general rule, use American spark plugs for American Cars and Japanese Spark plugs for Japanese cars. Since this is a German design Engine, would Bosch be a player here? IDK
 

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I was also looking to see if this was ever resolved. I have a 2014 Cruze Eco and the light started to go off around July 2018 (give or take a month, I didn't start taking notes until October). The light finally stayed on in December and at that time I had my mechanic do the 100,000 mile check. He didn't see anything.

In April, we decided to try a new catalytic converter. It was refurbished and the light came back on in less than a week. We replaced it again (with another refurbished, I think) and just a few days later the light was back.

Next they tried to reset some parameters (not quite clear on what was reset). Light came back on in less than a day. Even though they swore they checked the sensors, I had them replaced yesterday. This morning the light is back on.

Not sure what to have them look at next. I know the sparks are due in about 10,000 more miles, but I haven't noticed any problems with them.

Not sure what changing the coils might due.

The other thing I read was the engine temp sensor.

I've had more problems with this Cruze than one would expect, but fixing it seems to be cheaper than replacing it.

Thanks is advance for any suggestions.
 

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So I just had the factory PCV go out in the intake and that problem took out the valve cover with it. I did the XtremeRevolution PCV fix and replaced the valve cover and re-set the Check engine light last week. The light has not come back on yet (its been about 5 days/300 miles). I will try to remember to post back if/when it does. Maybe that PCV was on its way out for a while causing this code...? The car had 110k miles on it when the PCV went out.
 

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It is not apparent to me from the above posts, but I could have missed it. Pull your plugs, re-gap at .028, re-torque at 18 ft-lbs, no anti-seize and make sure the resister springs are not caught up in the boots. Also make sure you have no tears in the boots. If the boots are stuck, use a small screwdriver or pick with some dielectric grease on it to go around the outside of the boot and then possibly the inside of the boot to help aid in removal.

If the plugs look bad, consider these:

-BKR8EIX-2668 (iridium plugs), ~$25, expect ~10-15k regaps on these, ~40-50k overall life.
-BKR7E-4644 (nickel/copper plugs), ~$8, expect 15-25K out of these plugs, with a regap or two required at 5-8k intervals on stock tune.

read Hesitation Gone for more info on the plugs.
 

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Just another update... I have had the code steadily since my last update here at 110k miles. Now I am at 125k miles and it went away again.

There was a deal on "3M complete fuel system cleaner" and I have never put anything in my tank since I bought it brand new so I figured it couldn't hurt anything to run something in there so I got it. Its normally really expensive but apparently worth it since my CEL went away after running it for 3/4 of a tank. No other changes besides running this in my gas tank, I filled up at the same gas station as I always do with the same grade of fuel and same commute and everything.

I'll update this thread again if or when the light comes back on.
 
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