Jump to content

Random Misfire (P0300) and o2 sensor codes!!

LongrangeLauber

By LongrangeLauber
in Ask A GM Technician

 Share

Recommended Posts

Maine2500HD Enthusiast

Maine2500HD

Posted
Posted
2 hours ago, Jsdirt said:

NTK is normally really good. Owned by NGK, the spark plug company. Must've got some bad ones there - happens more than normal these days with every brand. I'll have to keep my eyes and ears open for more failures with this brand - could be a possible drop in quality.

 

The cat codes will only come back ones the cat monitor has run. No specific set time for that - it all depends on if you met the requirements for the cat monitor to run, normally cruise at 55 or higher for several miles, then a long deceleration event without touching the brakes. if you live in a congested area like I do up here in MA, it can take weeks to run.

It doesn’t really take much for a defueling event duration to read/set it. I was watching it in Live data. It can be as simple as a slight/brief lift off the throttle. The ECM will not allow the code(a) to be set during the first hour-ish? Of run time after a battery disconnect. That is to allow for a break-in/run-in of cats when they are replaced. That’s why I could make it go away for a while.

 

I’m seriously questioning if the NTK sensors are even spec’d right, or maybe were my boxed right? Had the right connectors but that doesn’t mean the sensors were right. They almost seemed like they wanted to run in a 2V range where it should only be a 1V range. 
 

I took all four back. It was wild the type of problems that they were causing. Entire bank 2 misfires, had communication errors between ECM and two different modules, varying voltage codes. Engine running in open loop for extended amounts of time (45+ min) Pretty nutty stuff.

 

 

  • Replies 62
  • Created
  • Last Reply

Top Posters In This Topic

Popular Days

Top Posters In This Topic

Popular Days

Popular Posts

shakenfake
shakenfake

Personally I would just go get a custom tune and tune the cat codes to be off and never worry about that again

shakenfake
shakenfake

Just need HPTuners and do it yourself

LongrangeLauber
LongrangeLauber

Posted Images

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted (edited)

You could've got counterfeit parts, especially if bought from Amazon or eBay. Starting to see it at RockAuto occasionally, too.

 

I've never heard of a time frame for setting cat monitors. Guys with dynomometers can run a drive cycle to a tee, and run every monitor successfully in minutes.

 

You should break in new cats, though - just idling in the driveway is sufficient for a specific period of time. Not something I do too often. Usually people punch them out and cheat the downstream sensor. They're too friggin expensive these days.

Edited by Jsdirt
Maine2500HD Enthusiast

Maine2500HD

Posted
Posted
1 hour ago, Jsdirt said:

You could've got counterfeit parts, especially if bought from Amazon or eBay. Starting to see it at RockAuto occasionally, too.

 

I've never heard of a time frame for setting cat monitors. Guys with dynomometers can run a drive cycle to a tee, and run every monitor successfully in minutes.

 

You should break in new cats, though - just idling in the driveway is sufficient for a specific period of time. Not something I do too often. Usually people punch them out and cheat the downstream sensor. They're too friggin expensive these days.

Over the counter from Napa to my hand. Highly doubt counterfeit.


The 1 hour applies to new vehicles (and in theory when the ECM/Battery has been disconnected long enough to reset.) I hadn’t heard of it either, but it came up on research, and explains why I could make the P0430 code go away for  most of the day when I’d disconnect the battery, when it would otherwise reset regularly. 
 

The drive cycle is fairly specific and a GM thing, and is an over the road test at speeds/loads for a specific amount id time. 
 

In the grand scheme of things $800 ish for any pipe with all three Cats isn’t awful…. But I’m not excited to spend it just the same. 

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted

You never stop learning in this industry, that's for sure! It's part of the reason I'm losing my fire for fixing modern crap. It's just too much info to store! 

 

Thanks for posting that - as long as I've been working on these, that's the first I've heard of that. Most of the vehicles with big time driveability complaints or major electrical problems that I see in here are from 2003-2005 lately. None of my customers own anything this new. The stuff is always changing! Impossible to keep up with the pace.

LongrangeLauber Senior Enthusiast

LongrangeLauber

Posted
  • Author
Posted

Turns out I do have NTK downstream sensors (I even had mentioned that earlier in this thread, completely forgot about it.) I just ordered up two GM Genuine Parts O2 sensors from Advance Auto that will be here sometime today (gotta love same day delivery!) for a little more than $60 for both (20% discount plus $20 off SpeedPerks coupon).

 

Not saying this will solve the issue, but for $60 it's worth a shot before dropping big bucks on a new Y-pipe assembly.

 

I looked into transferring to another address in a jurisdiction that does not require emissions. Unfortunately since my tags are already dead, and it is currently registered in a county that requires emissions, I would have to pass the emissions inspection before I could even register it elsewhere. Or maybe I'm just reading the VA DMV rules incorrectly. Who knows. But this is affecting how the truck drives somewhat, so I do want to get it resolved one way or another.

 

New Y-pipe assembly will cost me about $1550 (core charge included) to purchase. I cannot return my current Y-pipe for core unfortunately since the factory cats have been cut out and replaced.

 

I will continue to update this thread until I figure out the solution.

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted

Nothing is easy or cheap these days. Sucks! Good deal on the GM ones, though. Hope that fixes it.

  • 2 weeks later...
LongrangeLauber Senior Enthusiast

LongrangeLauber

Posted
  • Author
Posted

Well, installed the new sensors last week and no dice (wasn't getting my hopes up on that one.)

 

So, I ordered a new OEM catalytic converter y-pipe assembly (part #: 19420276) that I picked up from my local dealership. Just installed it this morning before a couple graduation parties I had to attend. No check engine light all day and stuck the code reader on it to see if the permanent codes that were stored had self cleared. Sure enough, all DTC codes are cleared and only one monitor hasn't run it's drive cycle and that's the EVAP system. It's looking like the OEM catalytic converter assembly did the trick for me.

 

After wasting so much time and money on this issue, it seems like I have finally resolved the issue.

 

A couple take aways I learned from this:

 

1) When having to replace catalytic converters, just go straight to the OEM part and don't waste your money on aftermarket cats (between install and the cost of the cats, I would have almost paid for the OEM converter assy with me installing it on my own)

 

2) Find a reputable shop that can properly diagnose the issue. Turns out the dealership was correct when they told me the aftermarket catalytic converters were not performing their duties properly, thus the codes remained set. But, the first shop I took it to said the aftermarket cats were performing their duties properly and thus they never revisited them as a potential issue.

 

 

 

I'm a little upset I had to pay for not only the OEM cat assy but also the aftermarket cats as well, and labor to install them, but I learned a valuable lesson for future vehicles. I can finally quit riding around on dead tags and not be worried about possibly getting a ticket for them.

 

Definitely a learning experience that I hope I never have to go back through again. I hope someone in the future finds this thread and it helps them out before they throw a bunch of money at their truck like I did.

 

Thank you all for chiming in with your thoughts and opinions along the way as I struggled (along with an independent shop) to diagnose this issue!

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted (edited)

Wow, what a shitshow! Glad you finally got it taken care of. Sucks you have to spend all this money all because of the damned government. Rotten SOB's - hope they all rot in hell.

 

My take is the downstreams ARE factored into fueling, otherwise there's no way a cat can cause a misfire code, unless it's completely stopped up solid. That's good to know, since I'd have never thought that in a million years. 

 

Thanks for sharing, CJ - some great info here!

 

This just reminded me of a '00 Jimmy I bought off eBay in '08. Had a cat code almost immediately after rolling off the transport trailer.  Had an aftermarket cat welded in. Someone warned me back then not to install another aftermarket one, so I bit the bullet and dropped $550 (That was A LOT of money to me for a friggin Y-pipe back then!) on a new Y-pipe / cat assembly. The 0420 was gone after that  ... then 15 more unrelated codes came up, and 2 years after I bought it, this is what I did to it out of  frustration. It's parts are all over the world now, lol! 

 

 https://postimg.cc/ZBD7mCt8

Edited by Jsdirt
shakenfake Senior Enthusiast

shakenfake

Posted
Posted
2 hours ago, Jsdirt said:

My take is the downstreams ARE factored into fueling, otherwise there's no way a cat can cause a misfire code, unless it's completely stopped up solid. That's good to know, since I'd have never thought that in a million years. 

Down streams are not factored into fueling.

 

Glad you got it figured out bud sucks but it is what it is.

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted (edited)
9 hours ago, shakenfake said:

Down streams are not factored into fueling.

 

Glad you got it figured out bud sucks but it is what it is.

DELETED ...

 

I went back and refreshed my memory - it was his upstream o2s that caused the miss originally.  So downstreams do not factor into fueling. Thanks for the info. :cheers:

Edited by Jsdirt
  • Like 1
LongrangeLauber Senior Enthusiast

LongrangeLauber

Posted
  • Author
Posted
8 hours ago, Jsdirt said:

DELETED ...

 

I went back and refreshed my memory - it was his upstream o2s that caused the miss originally.  So downstreams do not factor into fueling. Thanks for the info. :cheers:

Didn't have time to chime in earlier when I saw the notification but yes, this whole issue started with a failed upstream sensor.

 

Now that I know the damage that a failed sensor can do, as soon as I see a CEL come on and driveability suffer, I'm pulling over and parking it. Cheaper to pay a tow bill at that point 🤣

  • Like 1

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.

  • Forum Statistics

    250.5k
    Total Topics
    2.7m
    Total Posts

  • Member Statistics

    342,901
    Total Members
    8,960
    Most Online
    AlVeron
    Newest Member
    AlVeron
    Joined

  • Who's Online   5 Members, 0 Anonymous, 562 Guests (See full list)

  • Latest Articles

  • Posts

    • PunchT37
      OCI, not when but why?

      By PunchT37 · Posted

      When I was there, most to all did not have an hour meter. They just did 5000 miles on regular vehicles and 3000 on police stuff. The modern oil change monitors should take into account engine hours, weather, etc. I don`t use the monitor on my stuff. I pull the stick, look at it, smell it, rub it between my fingers, etc. That`s my oci.   I have had many engines. Some bracket race. No problems doing things my way. I was in the mechanic business for 30 yrs or so. I still do things the old school way. Don`t care who laughs at me.   Understand, I was in the main shop. We didn`t do oil changes or tires. We had a service station for that. I don`t remember the hours they used for tractors, lawn mowers, etc. Something in my head says 250 hours.
    • Chuck FB
      OCI, not when but why?

      By Chuck FB · Posted

      I don't know how far back vehicles had hour meters, be it driver accessible or diag accessible but was wondering if there was any rule of thumb your shop came up with in regards to an hour limit on engine oil regardless of the miles on the oil.    I know with construction or farm equipment its almost always based on engine hours for maintenance scheduling as no other metric really applies other than a seasonal time limit that one self imposes on items like engine oil.  
    • Chuck FB
      OCI, not when but why?

      By Chuck FB · Posted

      I'm not sure what to say on that mess but I will say that is an odd thing for that mechanic to speculate on as per assuming its been run out of oil a few times as the odds of that engine having instead piled up with a complete seizure would be very high if such events had actually taken place. However there is nothing saying that the oil has ever been changed although once again, what filter was on that engine as that would tell part of the story if its possible to figure out if its a factory installed filter or not. Too many items unknown and a lot of speculation, but regardless of that its one fubared mess that is mind boggling to see for a vehicle that new and its hard to imagine how it ever made it that far in life looking at the top of the engine.    His scanners, I've watched him before here and there and I'd have to say if I recall correctly that some of his scanning equipment is one or two steps up from a child's Exo Sketch 😋
    • PunchT37
      OCI, not when but why?

      By PunchT37 · Posted

      I agree. That`s a LOT of sludge for 12,000 miles. I tossed that out here since this is an OCI thread. There`s tons of people here that do not post.   I used to work on a city fleet. That includes police cars and fire trucks. Lesson is, not to only use the odo for oci. A police car has a ton of hours on the engine for the miles it shows. And, not just idling, directing traffic. They beat on these things.   Course, since it is a Kia, they were gonna use the "100,000 mile warranty" for their OCI.😉
    • AlVeron
      Manufactuer's Defect - Paint Failure - Cherry Red High Country 2021 Suburban

      By AlVeron · Posted

      CLASS ACTION SUITS?  Does anyone know if there is already a class action suit for the paint - which was to have been fixed, changed in after the 2020 GM vehicles?  Does it look like this?    Just started 3 weeks ago - No help from GM as of yet - Dealer will not assist in speaking with GM on my behalf. Confirmed it is the paint they use along with the way the put it on that causes it to fail.  Clearly a Manufacturer's Defect. 

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...