Random Misfire (P0300) and o2 sensor codes!!

[LongrangeLauber]

Okay this is driving me crazy as I can normally figure most things out myself. Truck is a 2014 Silverado 1500, 5.3L (L83)

 

I am getting a P0300 code as well as these o2 sensor codes: P0030, P0031, P0135, P0137

 

Truck was running 100% fine until Monday morning (6/21). Leave my house to head to work and I get on the main street to get to cruising speed. Truck pretty much feels like it goes into limp mode, I lose all power, for about 4-5 seconds or so. Then it downshifts to 2nd or 3rd, and I cruise most of the way to work without issue. Stop for coffee, hop in the truck, runs fine all the way to work, but about 2min from work I get my CEL on the dash. Didn't have my scan tool so waited until I got home. Pulled codes only for the upstream driver side sensor and then cleared them. They came back this morning, and now this evening the truck seems to be getting worse and almost sounds like it's about to stall out at times. That's when all the other codes popped up alongside them. 

 

Only thing I can think is there may be water in the fuel. Last time I filled up (Saturday, 6/19) I filled with the 88 octane stuff from Sheetz (believe it says up to 15% ethanol as opposed to 10% in the regular gasolines) and I still had a little over 1/4 tank when I filled up. I've ran that fuel for many thousands of miles with no hiccup (truck is FlexFuel capable) until this week. 

 

I picked up a new upstream o2 sensor tonight and that's when the truck started acting up more. On my way home from the parts store that's when I thought about possible water in the fuel, so I stopped at a different station and filled up with regular 87 octane; at this point I burned a little more than half a tank, added about 17 gallons on this fill up.

 

At cruise speeds it runs perfectly fine, will downshift when I hit the accelerator too, but sometimes it sounds like it is struggling trying to get to those cruise speeds.

 

Is it just coincidence that the truck started acting up after I filled up last? Or should I actually go ahead and replace the o2 sensor and see if that changes things? Would rather not just throw $$ at it in hopes of fixing it, but sometimes it beats having to drive all the way to the dealer plus taking time off from work.

 

Any input would be awesome, thanks all!!

 

 

[Jsdirt]

Wow, definitely interesting! I'm shocked MA doesn't have a system like this. 

 

Yeah I figured that would be at least a few hour drive one way. IMO, it would be well worth the effort given what you've been through so far. I'd wager it would end up cheaper for you in the long run over any dealer.

 

If you go for a full-throttle run up a long hill after the engine is warmed up, stop somewhere safe and get a whiff of the exhaust - it should just be like hot, moist air, and not really have any odor to it. Any rotten egg smell and there's an issue. But, this can happen with an active misfire, too, and not necessarily mean the cats are smoked. Scan tool o2 voltages are a better indicator of what is happening. 

[Maine2500HD]

2 hours ago, Jsdirt said:

Wow, definitely interesting! I'm shocked MA doesn't have a system like this. 

 

Yeah I figured that would be at least a few hour drive one way. IMO, it would be well worth the effort given what you've been through so far. I'd wager it would end up cheaper for you in the long run over any dealer.

 

If you go for a full-throttle run up a long hill after the engine is warmed up, stop somewhere safe and get a whiff of the exhaust - it should just be like hot, moist air, and not really have any odor to it. Any rotten egg smell and there's an issue. But, this can happen with an active misfire, too, and not necessarily mean the cats are smoked. Scan tool o2 voltages are a better indicator of what is happening. 

I think the CAT thing  by the dealer is B.S. The strange part about my issue, is that I can make it go away for a day or so by disconnecting the battery. But so far it continues to come back when it feels like it. Hooked it up to a high end diagnostic tool briefly this morning, with no codes(after having unhooked the battery and resetting it this morning so I could drive it), and we looked at the graphical voltage data from all four O2 sensors and as expected there were no anomalies at all. Everything is functioning as it should. We cleared all past/existing codes in the system which is more than I could do with my tool, and basically set a baseline. Going to keep running it and see if it returns. So far I have almost 90 miles on it since the reset this morning and no hint of a code. I'm leaning heavily to a wiring issues somewhere with an intermittent short causing it. I took out my scope and checked a few grounds and they are clean as a whistle so I haven't disconnected any of those and chased them yet. I'll keep you posted. I really doubt that you'll find the issue to be your cats.

[LongrangeLauber]

41 minutes ago, Maine2500HD said:

I think the CAT thing  by the dealer is B.S. The strange part about my issue, is that I can make it go away for a day or so by disconnecting the battery. But so far it continues to come back when it feels like it. Hooked it up to a high end diagnostic tool briefly this morning, with no codes(after having unhooked the battery and resetting it this morning so I could drive it), and we looked at the graphical voltage data from all four O2 sensors and as expected there were no anomalies at all. Everything is functioning as it should. We cleared all past/existing codes in the system which is more than I could do with my tool, and basically set a baseline. Going to keep running it and see if it returns. So far I have almost 90 miles on it since the reset this morning and no hint of a code. I'm leaning heavily to a wiring issues somewhere with an intermittent short causing it. I took out my scope and checked a few grounds and they are clean as a whistle so I haven't disconnected any of those and chased them yet. I'll keep you posted. I really doubt that you'll find the issue to be your cats.

Yeah I can undo my battery for about 30min and it does a full reset of the ECM and the codes will go away for a day or two but come back.

 

Goodluck on your diagnosis, I’m getting tired of spending money on this thing. If it doesn’t pass through one of those rapidpass units then I’ll just register it in a different county that doesn’t have emissions.

[Maine2500HD]

35 minutes ago, rdnckhntr94 said:

Yeah I can undo my battery for about 30min and it does a full reset of the ECM and the codes will go away for a day or two but come back.

 

Goodluck on your diagnosis, I’m getting tired of spending money on this thing. If it doesn’t pass through one of those rapidpass units then I’ll just register it in a different county that doesn’t have emissions.

Your drivability never suffers? I'm basically forced to reset the ECM sometimes because it stumbles, stalls, and flashes the MIL light and it's pretty  much undriveable for a bit. It will sometimes snap out of it but not always. I'm impressed you've been able to tolerate it this long. Not knowing what it is or being able to diagnosis just irritates the s**t out of me lol

[LongrangeLauber]

12 minutes ago, Maine2500HD said:

Your drivability never suffers? I'm basically forced to reset the ECM sometimes because it stumbles, stalls, and flashes the MIL light and it's pretty  much undriveable for a bit. It will sometimes snap out of it but not always. I'm impressed you've been able to tolerate it this long. Not knowing what it is or being able to diagnosis just irritates the s**t out of me lol

That’s exactly how it started. CEL came on and was flashing and the truck stuttered and slammed back into gear real violently, then CEL went solid.

 

It did it intermittently for about 100 miles/ 2 days until I had a chance to diagnose it.

 

Confirmed it had a bad upstream O2 sensor. Replaced and the code for sensor went away but the p0420 stayed and eventually a p0430 showed up within a couple months.

 

Thats when I took it to the shop and had them replace both catalytic converters with Magnaflow ones. Codes persisted and shop said it was O2 sensors. So they replaced all four sensors and codes came back shortly after leaving the shop.

 

After that is when I took it to the dealership.

[Maine2500HD]

I did a full swap of all four sensors, codes and original behavior all keep coming back. Swapped some of the old sensors back in, and have moved new ones around, and none of the sensor movement caused a change in symptom. My first code that made me start down this road was a P0430, which still comes back intermittently. Second code was for Bank 2 Sensor 2. The shitting runny and flashing CEL didn't happen until I had all four new sensors in. Now it recurs regardless of the combination of new and old sensors and after watching voltages, they are all behaving like normal today. Diagnosis is going to be interesting because the failure is intermittent.

[Jsdirt]

6 hours ago, rdnckhntr94 said:

That’s exactly how it started. CEL came on and was flashing and the truck stuttered and slammed back into gear real violently, then CEL went solid.

 

It did it intermittently for about 100 miles/ 2 days until I had a chance to diagnose it.

 

Confirmed it had a bad upstream O2 sensor. Replaced and the code for sensor went away but the p0420 stayed and eventually a p0430 showed up within a couple months.

 

Thats when I took it to the shop and had them replace both catalytic converters with Magnaflow ones. Codes persisted and shop said it was O2 sensors. So they replaced all four sensors and codes came back shortly after leaving the shop.

 

After that is when I took it to the dealership.

I had forgotten you had cat codes. Unfortunately, the dealer is right - OE replacement is the only fix (besides registering in another county).

 

I had a 0420 code in a '00 Jimmy I had 14 years ago - eBay purchase ... from a car dealer. Couldn't have made a worse decision there. Anyway, the vehicle arrived and immediately set a 0420 code (among 100 other issues). Had to buy a whole Y pipe with the single cat in it for $500 ... back then! I can only imagine what that Y-pipe is today. That got rid of the code. That was all because someone installed an aftermarket cat prior to me buying it.

 

If your Sensor2 02's are switching like the upstreams are, and the sensor is good, that's a bad cat. Those numbers should remain steady from between 600-800 mV with minimal variation. If not, the PCM flags a cat code.

 

Sounds like you fixed the driveability problem with the new upstream 02s.

Edited April 29, 2022 by Jsdirt

[shakenfake]

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

[Jsdirt]

AMEN!

 

Only problem is around here I've heard many went out of business due to the new regime in office. Guess the EPA has been swinging the hammer ...

Edited April 29, 2022 by Jsdirt

[shakenfake]

Just need HPTuners and do it yourself

[Maine2500HD]

On 4/28/2022 at 12:43 PM, rdnckhntr94 said:

Yeah I can undo my battery for about 30min and it does a full reset of the ECM and the codes will go away for a day or two but come back.

 

Goodluck on your diagnosis, I’m getting tired of spending money on this thing. If it doesn’t pass through one of those rapidpass units then I’ll just register it in a different county that doesn’t have emissions.

I’ve since learned that when you disconnect the ECM, it will prevent the P0430/420 codes for roughly and hour of run time. This was by design to be able to allow for CAT break ins to be done without setting codes.

[Maine2500HD]

Well, I solved it. Garbage NTK sensors. I put all the original Denso sensors back in and the problem went away. I don’t know what’s up with the new NTK sensors but they were causing al kinds of crazy issues with voltages and they were so far out the truck was defaulting to Open Loop for hours at a time and running off of tables. When it would try to cycle back to closed loop it would stumble and misfire Bank 2 badly. It caused some weird “no communication” errors with a couple different modules when it was in misfire mode. 
 

fingers crossed, but the issue hasn’t come back since I out the original Denso sensors back in.

 

I do think the P0430 will come back. Watching the upstream and downstream sensor graphs, it’s apparent that the cat isn’t 100% ok. There are times the downstream mirrors the upstream fluctuations, though not super often. The Bank 2 sensor also has a little more fluctuation than Bank 1 sensor 2.

 

I did plugs and wires last fall and discovered that the Bank 2 components were all original at 120k but bank 1 had been changed. Was having misfires on bank two. I think that stress probably led to the degradation of the Bank 2 Cat. Planning on replacing it, soon.

 

 

Edited April 30, 2022 by Maine2500HD

[LongrangeLauber]

19 minutes ago, Maine2500HD said:

Well, I solved it. Garbage NTK sensors. I put all the original Denso sensors back in and the problem went away. I don’t know what’s up with the new NTK sensors but they were causing al kinds of crazy issues with voltages and they were so far out the truck was defaulting to Open Loop for hours at a time and running off of tables. When it would try to cycle back to closed loop it would stumble and misfire Bank 2 badly. It caused some weird “no communication” errors with a couple different modules when it was in misfire mode. 
 

fingers crossed, but the issue hasn’t come back since I out the original Denso sensors back in.

 

I do think the P0430 will come back. Watching the upstream and downstream sensor graphs, it’s apparent that the cat isn’t 100% ok. There are times the downstream mirrors the upstream fluctuations, though not super often. The Bank 2 sensor also has a little more fluctuation than Bank 1 sensor 2.

 

I did plugs and wires last fall and discovered that the Bank 2 components were all original at 120k but bank 1 had been changed. Was having misfires on bank two. I think that stress probably led to the degradation of the Bank 2 Cat. Planning on replacing it, soon.

 

 

Will have to see if any of my sensors are NTK branded. Pretty sure my upstreams are Denso sensors, cannot recall what the downstream sensors are though.

[Jsdirt]

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.

Edited April 30, 2022 by Jsdirt

[Maine2500HD]

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.