# Code P0420 Causes



## Blasirl (Mar 31, 2015)

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 _

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


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## RichLo1 (May 31, 2018)

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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## msgongora (Jun 12, 2015)

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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## Blasirl (Mar 31, 2015)

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

Also asked here


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## msgongora (Jun 12, 2015)

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.



Blasirl said:


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


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## RichLo1 (May 31, 2018)

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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## Blasirl (Mar 31, 2015)

It is possible it is the coils causing an issue.


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## RichLo1 (May 31, 2018)

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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## power4utoo (Dec 11, 2018)

RichLo1 said:


> 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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## RichLo1 (May 31, 2018)

power4utoo said:


> 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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## deadsmiley (Nov 3, 2014)

RichLo1 said:


> 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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## RichLo1 (May 31, 2018)

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 ccasion14:


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## power4utoo (Dec 11, 2018)

RichLo1 said:


> 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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## Akenta (Aug 1, 2017)

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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## Nissansentra (Apr 22, 2018)

Did u guys ever get his figured out? I'm in the same spot. Same code replaced o2 and cat and still no luck.


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## RichLo1 (May 31, 2018)

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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## RichLo1 (May 31, 2018)

CEL just came back on this morning


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## Blasirl (Mar 31, 2015)

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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## RichLo1 (May 31, 2018)

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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## Shroomie (Jan 16, 2017)

RichLo1 said:


> 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.


I use the Chevron with techron stuff or seafoam in the gas tank. Haven't had any issues or that specific check engine light... this car is actually quite weird as I had boost/vacuum leaks with the intake manifold gasket, throttle body gasket and valve cover gasket and had surges at idle but never a check engine light on this dang car.


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## Blasirl (Mar 31, 2015)

For those of you who don't want to spend $500 plus for the LS7 upgrade, try this:


MSD Coil pack at BNR: http://store.badnewsracing.net/MSD-Ignition-Coil-2011-2016-GM-14T_p_663.html

For less than the cost of an OEM pack, but better.


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## RhoyPE (Feb 5, 2020)

RichLo1 said:


> 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.


Hi, Rich. i have the same code and 2 extra codes: P0171 & P013A. So i'd like to know if the last action worked. the mechanic saidme it could be the fuel pump but I don't know how true it could be (based on the readings he saw on the scanner).
regards


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## Akenta (Aug 1, 2017)

Looks like the last time I posted something was back in May. After the refurbished catalytic convertor didn't work, the auto shop looked around to see if they could find a solution. The only they found was to replace the convertor with a GM convertor. I said to go ahead and found out it was on back order so I had to wait a few weeks. Came into the shop right before the GM strike and they put it on. That was back in September, and I'm happy to say the light has not come back on (though I hold my breath every time I start the car and was afraid to post here in case it jinxs it).

I think this is a problem GM caused and only they know how to fix it.


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## power4utoo (Dec 11, 2018)

RichLo1 said:


> 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.


WOW "3M complete fuel system cleaner" ! Did it work for a long time? I still have my engine light on... LOL


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## gannman2000 (Jan 28, 2019)

So here is a weird one.............my CEL has been on for over a year now, with P0420 being the main code that would not go away (other codes, like 'random misfire', were cleared with new plugs and coil pack). I live in Taxifornia, and they want a ludicrous sum of money for a 'CARB approved' catalytic convertor ($1300 !!!! vs about $300 in the other 49 states), so that's why I have been living with the CEL being on. Anyhow, my 2014 Cruze 1.4 ECO started consuming coolant the last few months, with no obvious leakage observed on the ground under the car, and only the rare occasional odor. I finally got tired of topping off the coolant reservoir bottle 3 times a week, so I had my (trusted) mechanic take a look; he installed a new radiator, upper and lower hoses, thermostat housing, and coolant overflow bottle hose. Lo and behold, the CEL was not only off after the repair, but so far it is STAYING off. I am scratching my head trying to understand how a coolant system issue could throw up a P0420 code. Thoughts ?


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## Dre661 (Sep 22, 2020)

Hey guys. Experiencing same issue. P0420. I've replaced the O2 sensors, catalytic, the plugs, and the coil. I've spent almost $2,000. and the code keeps coming back between 1 day and a month after every repair. I'm at a loss, I don't know what else it could be.


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## Jeffreyj (Oct 2, 2020)

Hi guys same issue, but a sonic. Do all the recommended replacements up to 100,000 miles plus a new cat at 95,000 and timing belt at roughly 105,000. Major issues decided to get a case # with GM no help like the do not care. Almost as if designed to have major head aches to make you dump it to purchase new????? Mechanic did most CEL light work used mostly GM Parts with consistent CEL light issues after and says running fine ignore the p0420 code, but if another code comes up let him know. Really disappointed 95,000 mile star, and p0420 problems for a little over 10,000 miles major ??????'s


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## Katie K (Feb 1, 2021)

Hello please help, I have a 2013 Chevy Cruz 4 cylinder turbo, I have replaced the catalytic converter 2 months later the light came back on with the same code, i brought it to the shop and they said the converter looked fine not sure what they did to test it but then they said to replace the o2 oxygen sensors, so I did, 3 days later light came back on, then went back they cleared history, 5 days later the code comes on again, the car still feels sluggish?! can the shop test the parts to make sure they are working i did not have the shop fix it, it was too expensive but i took there suggestions and bought the parts and had someone put them in?! the light stays on until i bring it to shop they clear it 5 days later the light comes back on


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## Wesley30021 (Jun 23, 2021)

Katie K said:


> Hello please help, I have a 2013 Chevy Cruz 4 cylinder turbo, I have replaced the catalytic converter 2 months later the light came back on with the same code, i brought it to the shop and they said the converter looked fine not sure what they did to test it but then they said to replace the o2 oxygen sensors, so I did, 3 days later light came back on, then went back they cleared history, 5 days later the code comes on again, the car still feels sluggish?! can the shop test the parts to make sure they are working i did not have the shop fix it, it was too expensive but i took there suggestions and bought the parts and had someone put them in?! the light stays on until i bring it to shop they clear it 5 days later the light comes back on


Hello I too am experiencing the 420 code after replacing converter and O2 sensors. I have found tho that the PCV valves in the air intake manifold can go bad as well as the diaphragm on the valve cover causing this code to appear. I am going to replace them and will leave an update but I would have those checked as they are a common failure on this vehicle


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## Wesley30021 (Jun 23, 2021)

Check the pcv valves and the valve cover


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## Jessikared97 (Jun 2, 2017)

Wesley30021 said:


> Check the pcv valves and the valve cover


Has anyone else had this fix work? I had a warranty repair on my PCV Valve cover @ ~60k. Just wondering because every single person on here seems to have found a different way to fix this **** code and I REEEALY dont have 2-3k to throw at the wall and see what sticks.

What did you have to have replaced? The valves ot the cover?

(Ps 2015 1.4 Turbo ~115k been fighting with code since 2019. Would come on once a year and I would clear it to see if it came back on (only when over 90° outside) but has come on twice this year. Replacing the upstream O2 sensor kept it off for like 4ish weeks. Mine is specifically p0420 (bank 1) if that matters)

Thanks!


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## Wesley30021 (Jun 23, 2021)

I found a technical service bulletin that stated if the 0420 code appears to check the intake manifold pcv and valve cover before changing the converters. If you google it I’m sure it will come up. Like you said I threw 2 grand at mechanics saying fix this and fix that and none of it worked. But if you YouTube it will show how to check the air intake manifold and valve cover because they are notoriously known for failing together. When this happens the fuel and air ratio is thrown off which will cause the car too run lean or rich and make it think that there is something wrong with the converters triggering the code. I just received and installed mines a few days ago tho. So far so good but if anything changes I will update


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## Wesley30021 (Jun 23, 2021)

O and when u had the valve cover fixed they should have checked the manifold so I would double check if they did because as I stated both are known to fail together on this vehicle and when you order one part it even comes with a recommendation that both are inspected


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## guuyuk (Nov 12, 2015)

I've had my CEL going on/off with P0420 for the last 6 months or so. With the current state of affairs, I've been working from home so most of my driving has been within 10 miles of home. Last time I went in to get a code reader to see if anything new had popped up, the counterperson suggested that I take a few longish (30 minutes or more) drives to get the car fully warmed up. I went ahead and drove across town a couple of times, and after that the CEL cleared itself again. Not that it's the only issue that can cause that code to trip, but I'll keep it in mind when it happens again.


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## Slacker (Aug 12, 2021)

Any resolution for this? Mine is a 2015 Cruz Same mileage same issue?


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## vexirae (Aug 19, 2021)

RichLo1 said:


> 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.


I know it's been a very long time so your issue may have been solved, but I wanted to add my experience in case it can help someone else....
it is apparently quite common for the spark plugs to become loose in the Cruze!! for me it manifested in a chirping noise that was almost like a squeak or a beep, speeds up when you hit the gas. it is the reason my car gave the P0420 code 
I figured it out after watching several videos of the same sound on YouTube, the chirp was gone once we tightened the plugs and the code hasn't come back yet! crossing my fingers


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## vexirae (Aug 19, 2021)

Nissansentra said:


> Did u guys ever get his figured out? I'm in the same spot. Same code replaced o2 and cat and still no luck.


mine was loose spark plugs!


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## Blasirl (Mar 31, 2015)

Slacker said:


> Any resolution for this? Mine is a 2015 Cruz Same mileage same issue?


Welcome aboard!

Are you trying to ask someone in particular about this?

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


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## Blasirl (Mar 31, 2015)

vexirae said:


> I know it's been a very long time so your issue may have been solved, but I wanted to add my experience in case it can help someone else....
> it is apparently quite common for the spark plugs to become loose in the Cruze!! for me it manifested in a chirping noise that was almost like a squeak or a beep, speeds up when you hit the gas. it is the reason my car gave the P0420 code
> I figured it out after watching several videos of the same sound on YouTube, the chirp was gone once we tightened the plugs and the code hasn't come back yet! crossing my fingers


Welcome aboard!

Yes it is/was very common.

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


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## power4utoo (Dec 11, 2018)

gannman2000 said:


> So here is a weird one.............my CEL has been on for over a year now, with P0420 being the main code that would not go away (other codes, like 'random misfire', were cleared with new plugs and coil pack). I live in Taxifornia, and they want a ludicrous sum of money for a 'CARB approved' catalytic convertor ($1300 !!!! vs about $300 in the other 49 states), so that's why I have been living with the CEL being on. Anyhow, my 2014 Cruze 1.4 ECO started consuming coolant the last few months, with no obvious leakage observed on the ground under the car, and only the rare occasional odor. I finally got tired of topping off the coolant reservoir bottle 3 times a week, so I had my (trusted) mechanic take a look; he installed a new radiator, upper and lower hoses, thermostat housing, and coolant overflow bottle hose. Lo and behold, the CEL was not only off after the repair, but so far it is STAYING off. I am scratching my head trying to understand how a coolant system issue could throw up a P0420 code. Thoughts ?


Wow, mine is doing that too. I also lose power whenever I accelerate with some determination, then all of the sudden the engine bogs down and loses 80% of it's power. Then I back it off and it seems to go back to the way it was. I noticed it is worse when it is hot, say over 80 degrees, and runs a lot better at that when it is cold out. The coolant usage is quite curious as well. No coolant in the, thank goodness. I saw one video on youtube where a guy found a leak at his flex-pipe, which is part of the cat system.https://youtu.be/jngmRVXCoV4 I haven't got a chance to peak at mine. I also found a guy that found oil in some connectors, however, he didn't bother to identify the parts he was talking about, and I don't know enough to go by what the heck he is pointing at or what he is saying to figure it out.


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## jharmon089 (Oct 26, 2021)

I had the same issue with my Cruze, I watched this and it made the code make sense. For whatever reason the code corrected its self but follow the 3 vids he has on the Cruze!


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## Hillbillypatriot (Dec 5, 2021)

Blueburner said:


> 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?


_ i have had same issues. Ive changed the coil pack and still no help. But i just watched a video about the catalytic converter. He tried to use aftermarket converter and it still wont clear the light and he found that you almost have to use the OEM converter and not skimp on the price. He showed tthesize difference and the standards on how these things work now. The aftermarket ones cant heat up quick enough to keep the engine running right. He is going to update the video as soon as he gets the new OEM part on. I guess i m Going to go ahead and order a new one. Im tired of chamging parts and getting nowhere. Its just hard to believe that the converters dont last longer._


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## stevezeilman90 (11 mo ago)

Blueburner said:


> 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?





Hillbillypatriot said:


> _ i have had same issues. Ive changed the coil pack and still no help. But i just watched a video about the catalytic converter. He tried to use aftermarket converter and it still wont clear the light and he found that you almost have to use the OEM converter and not skimp on the price. He showed tthesize difference and the standards on how these things work now. The aftermarket ones cant heat up quick enough to keep the engine running right. He is going to update the video as soon as he gets the new OEM part on. I guess i m Going to go ahead and order a new one. Im tired of chamging parts and getting nowhere. Its just hard to believe that the converters dont last longer._


Just want to let everyone know. Ive got the light to go away from replacing the turbo. There was a leak in the turbo causing the light to come on. I gor a junk yard turbo for 70 bucks put it on and light is gone hope this helps


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## gsalisbury13 (10 mo ago)

stevezeilman90 said:


> Just want to let everyone know. Ive got the light to go away from replacing the turbo. There was a leak in the turbo causing the light to come on. I gor a junk yard turbo for 70 bucks put it on and light is gone hope this helps


How did you go about diagnosing this? I’ve been battling this code for a hot minute now


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## Kingalfredo (5 mo ago)

Anyone else have a update on this? I'm dealing with the same issue with my 2014 Chevy Cruze 1.4 eco. No luck on the diagnosis still :/


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## Taxi.Dad (6 mo ago)

Was having a different issue where I'm on the expressway driving about 70 mph when I'd lose acceleration (as though it's not getting gas). I'd pump the pedal a few times and the car would pick up, but blew smoke (bluish white, burning oil). Possible causes mentioned were air leaking from the valve cover, PCV valve or oil cap. Replaced the cap with a new style (GM / Delco, snap in with long neck) before I went to work. By the time I got to work, the check engine line came on with the P420 code. Just now put the original cap back on and will let you know if it goes away.


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## Taxi.Dad (6 mo ago)

After putting the original oil cap back on, the check engine light was off the next morning. It stayed off for the next few days, so I reinstalled the new cap as a test to see if the light comes back on. This time, however, the new cap seemed to install much easier (before, it seemed like I had to torque it a bit) and this time I heard a click when it went into place. Been driving a half day and the check engine light has not returned. Guessing I previously had the new cap installed cockeyed and that cause my P420. For those who are interested, here is the old oil cap on the left and the new "standard" oil cap on the right.


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## redlinefidelity9 (5 mo ago)

For those of you with P0420 with any combination of other emissions codes, if you have a PCV problem you need to replace the intake manifold, intake manifold AND the PCV hose; dorman 615-380KIT. Right now with code SEPT1 at advanced auto parts it's about 280. The PCV hose contains a rubber check valve that hardens and also gets crudded up with carbon and sticks open not to mention the hose also turns into hard rubber and cracks. 
Other items to also purchase are the o-rings on the dipstick, oil cap, and change/check your plugs. The spark plug boots have a nasty habit of hardening and allowing moisture in, corroding the hell out of the springs and resistors, advanced auto also sells boots and resistors for about 40 bucks for the set. 

1. The evap and emissions system on this car work very well, however...
2. The fickle PCV system absolutely wreaks havoc on literally everything if you don't fix it quickly. If you pull your dipstick and the engine stumbles significantly you can bet there's an issue. 

Additionally, if your PCV issue was severe enough it will eventually damage the front and rear crank seals; the front crank seal contributing to the chirping noise everyone thinks is the serpentine belt or tensioner; the rear will just leak. Third order issues are oil in the boost recirculation valve and leaky cam position actuator seals, and even evap codes (p0442, etc) due to excessive carbon accumulation inside of the evap check valve and solenoid; both of mine were trash and wouldn't hold vacuum. 

Now concerning the lean bank and cat performance codes, tech notes also state to replace the coolant temp and O2 sensors together before the cat. 

Good luck


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## Taxi.Dad (6 mo ago)

Taxi.Dad said:


> Was having a different issue where I'm on the expressway driving about 70 mph when I'd lose acceleration (as though it's not getting gas). I'd pump the pedal a few times and the car would pick up, but blew smoke (bluish white, burning oil). Possible causes mentioned were air leaking from the valve cover, PCV valve or oil cap. Replaced the cap with a new style (GM / Delco, snap in with long neck) before I went to work. By the time I got to work, the check engine line came on with the P420 code. Just now put the original cap back on and will let you know if it goes away.


Just a follow up for those reading this thread that may have something similar. I recently disposed of the car and told the new owner of this issue. He got back to me and said his mechanic replaced the third-party valve cover and PCV valve with an OEM one. That resolved the issue for him.


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