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2014 lml p0420 code

25K views 40 replies 9 participants last post by  CMonclova1 
#1 · (Edited)
I am on a road trip that started in south Georgia and I am on my way to Shiocton Wisconsin. I am towing an 18 ft flatbed trailer with a light load. 3000lbs including trailer. There are no mods on the truck. I am half way through my last tank of fuel.

I stopped at rest area and when I started the truck everything appeared fine. I saw the check engine lamp come on. I pulled off the highway to check fluids. Not finding anything, I drove on to a safer place to take a look and get my code reader that was packed away.

I came up with these codes:
P0420 three times.
P220b
U029d
U029e
P2610

I will attempt to clear the codes with my tool but I think a couple are permanent codes.

I'd like to know if I can continue to drive. Am I looking at a possible breakdown? Or is this just an emissions related issue?

Any information will be appreciated. Getting back on the road in 24 hours.
 
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#2 ·
Fill out your signature with info on your truck. That will help us fill in the blanks.

It looks like you’re CAT is sooted up or bad and your NOX sensors are faulty. Im afraid you may have succumb to the good ole emissions failure. This will most likely limit you’re speed if you continue.
 
#3 ·
Thank you. I reset the codes with the exception of the perm p0420 code. I will continue with the trip tomorrow. We will see how it goes. No power issues yet.
 
#4 ·
Has your truck gone thru the regen process on a regular basis?



This information is published for my 2008 LMM truck - yours may be different:

  1. Inspect for the following conditions, which may cause a diesel oxidation converter (DOC) to degrade:

    • Off Road Fuel or Red Dye Fuel
    • Low quality B-20 fuel
    • Fuel Containing high sulfur content
    • Engine oil or coolant consumption
    • Leaking fuel injectors

  1. Inspect the DOC for the following conditions:

    • Physical damage or alterations
    • Internal rattles caused by a damaged catalyst substrate
    • Exhaust leaks before or after the DOC.
    • If a condition is found, replace the DOC.

  1. If all exhaust system inspections are normal, replace the DOC.
 
#11 ·
Has your truck gone thru the regen process on a regular basis?



This information is published for my 2008 LMM truck - yours may be different:

  1. Inspect for the following conditions, which may cause a diesel oxidation converter (DOC) to degrade:

    • Off Road Fuel or Red Dye Fuel
    • Low quality B-20 fuel
    • Fuel Containing high sulfur content
    • Engine oil or coolant consumption
    • Leaking fuel injectors


  • Non-ULSD fuel was a concern back in 2008, but it is not illegal to manufacture or sell it in US or Canada.
    During the conversion of the N.A. fuel supply there was a period of time both were available, the as the conversion was 'phased', there was a period of time when non-taxed (and usually dyed to identify it) fuel was LSD while rod fuel was ULSD.

    Today, all US/Can fuel is ULSD.
    Non-taxed fuel is still typically dyed so the 'revenuers' can identify it if/when they are doing roadside checks.

    (Diesel that is not ULSD can still a concern for those that might be travelling in some areas of Mexico)
 
#5 ·
It went through at least one regen since I left south GA. I only noticed because of the higher than normal idle at a traffic stop. After the codes I saw it go through a regen on my scan tool. It showed, on active 100%. When it was finished it said off passive 49% -52%
 
#7 ·
Finding someone competent is the problem. Especially since I am on the road. I can see many of the sensors related the cat and dog but I have no idea of what normal readings look like.
 
#10 ·
GM dealer, yes. I was told it needs the nox sensor 2. The problem is, if it fails, I will be on the highway for 1200 miles and stuck where if it fails. Has a box sensor ever fixed this kind of problem?
 
#14 ·
Thanks. I will take your advice. My scan tool did show a percentage on the dpf at 48 to 52. That is after a normal regen. It was at 100 before the regen when the fault first came up. At my job we have protocols as well, but it is my experience that techs take the easy path. Experience also tells you what the most likely fix will be that vary from the protocol standard. Maybe my tech will have some experience on a Duramax.
 
#15 ·
How many miles are on your truck? I've repaired numerous P0420 codes with a new 9th injector or indirect injector and a stationary regen after the replacement. I've replaced the indirect injector on 4 different LML trucks at around the 120,000 mile mark and it's repaired every one of them. Just did one on Tuesday. Not saying that's the issue on yours but it's possible. The injector gets clogged up and dribbles fuel into the exhaust stream instead of spraying and then it can't get hot enough to do a successful regen.
 
#16 ·
99985 miles when the codes first came up. It has been 3000 miles since I've added any def and it still says ok. Maybe I should top it off to see if it is using any.

Most of the trucks life has been on the highway. But this summer I was hauling logs out of the woods. It idled a bit to keep the ac on while I loaded the trailer. Maybe that is how this issue started. I am just now reading that idling is not a good idea.
 
#17 ·
Well they indeed replaced nbr 2 nox sensor and indeed failed after just under 100 miles. Good thing I was able to dump the trailer and gear off before taking it back to the same service center in Oshkosh.

Same codes: u029d u029e p0420 p220b these are pending and permanent codes.

Have to fly home for work so we will see how it goes in a couple of weeks.

Thanks GM, thanks EPA!
 
#20 ·
Not being able to inject DEF as nothing to do with regen success or lack of.

Plugged def injector could cause high NOx level problems, but the 9th injector would still be able to inject diesel for the regen's to occur and burn soot from the DPF.


The so called '9th injector' injects fuel into the exhaust for regen.
The 'DEF injector' injects DEF for NOx reduction -- whenever it is running.
 
#19 ·
Two wires rubbing together near x107 may be the cause. This large connector came loose from its mount and caused damage to two wires , either b10 and c10 or b1 and c1. These are nox sensor power and ground wires for nox 1 and 2. No word from the dealer yet. I may just go there on Tuesday and pick it up ready or not. I did tell them about the two wires.
 
#21 ·
Thank you. I was was mistaken on what my son was talking about. He was talking about the 9th injector. And he told me it may not be my nox issue, unless the dpf was clogged. I am still learning how all this works. I hope my issue is just the chafed wires.
 
#22 ·
Well... no contact with the dealer as of yet. I did call them on Saturday but my truck was not looked at yet. I left a msg with my service advisor since he was off for the week. Another service advisor looked at my service record and told me it hasn't been touched yet. That would have given them 3 full days with my truck. I sent an email to the generic dealer email and was returned in 24hrs by the general manager with a note stating that my msg was sent to the service department.

I am flying back to ATW (Oshkosh) to pick up my truck . When it breaks down again, I hope it is near a competent Service center. I am really hoping for the two chafed wires to have been the whole problem.

For anyone who cares at GM, the x107 plastic connector support is a very poor design. When it fails the harness sags and the wire harness rubs on a bolt below it. These two wires are what I believe to be nox2 power and ground wires b10 and c10.
 
#23 ·
The dealershop got my message finally! It is amazing that after I pointed out the two damaged wires that they find another issue that they didn't find the first time. Now the reductant pump in the def tank is bad. Would there be a code related to a bad def pump? I did tell him that tank unit was replaced under warranty at 80k miles. Now at 100k it has failed. GM is making me a proud owner.

There is a question in the above rant. Is there a code related to the reductant pump?
 
#24 ·
The dealer said that I needed a new def pump. It was 18f that day, I'm just wondering it the def was starting to gel and it really wasn't an issue. There was no mention of fault codes related to the pump. We will never know.

Back on the road again for a 300 mile test run. Only have a p0420 perm code and three more readiness parameters.
 
#26 · (Edited)
Seems like maybe mixing up DEF problems and regen problems.

DEF freezes at 12F.
Truck should run fine even with temps below that.
Built in heaters will run after the truck is started.
18*F should have nothing to do with your problems.


Even if there is/was a def tank issue, the P0420 is a different problem)

Regardless, P0420 is related to HC (hydrocarbon (diesel)) conversion rate not a DEF problem.

As wiilydmax indicated, there is likely some problem with the 9th injector (regen injector) not spraying correctly, so the fuel isn't being converted to enough heat to get the regen done.
 
#25 ·
I drove 300 miles and only a generic permanent p0420 code remained and cel was off. I drove it again today and 10 miles into the trip the cel came back on. It showed p0420 pending p0420 current and p0420 permanent. The nox sensor faults did not return after the wire harness repair. I did not get the service exhaust system with the 99 miles until 65mph.

How long do you think I can drive with the p0420 code? I reset it and it came back after 20 miles. I would like to get it home 1200 miles.
 
#27 ·
Well it is not me mixing up the issues. It is the certified gm tech. I never saw a def pump code or had an issue with it. I had to fly home and leave the truck with the dealer. They told me I had a problem with the pump and there is no way to drive it with the problem. They took care of it ( that I never saw) but I still have the p0420 code. Does the p0420 put you in limp mode or limit your speed? If not I would attempt to get home and deal with it there. I am thinking the nox sensor harness ( power and ground wires) was the reason behind the service exhaust system and speed limitation.
 
#28 ·
I am thinking the dealer tech doesn't really know what's going on. I didn't see any codes related to the def pump. My guess is that maybe they did a test of the pump /def system and the pump failed the test. Idk. The egts are in the upper 400s to lower 500s while highway cruising. All egts were about 900/1000 during a normal regen. I dont know what they read cold yet. I will check today. I would like to replace the 9th injector when I get home. I'm not against replacing the scr cat either if that is where the p0420 lies. Or is it the dpf where the p0420 originated. Nox sensor readings are in ppm are at 8-10 range ( hwy driving )and they both vary with throttle moments. The nbr 2 nox sensor was replaced erroneously due to the wires that were chafed.

I'm guessing that when the nbr 2 nox sensor wires were shorted, neither nox sensors were working. So the scr cat or the dpf sooted up. Could this be my problem?
 
#29 ·
I got the truck home. I got the cel as I started my trip. I cleared them and the truck immediately started to regen. The truck ran well pulling the trailer. The cel came on again after 1000 miles. I cleared the code again and the truck started a regen. This time it was in regen for over an hour. Nbr 1 egt was 600 ish 2,3 and 4 made it to 1000f for most of the regen. I did notice the dpf dpsi was 3.5 when at full throttle. After the regen it was at 1.5 psid. Also for the first time since my problem started, the dpf finally dropped down to 32% . It was always at 100%. Cel did not come back on after the last 3 hours. No pending codes just the p0420 permanent code. I still have a few readiness monitors to be satisfied .
 
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#30 ·
OP, I'm sorry to hear about the troubles that you are having. I was thinking about getting a 2015 LML Duramax but I'm not willing to take the chance on the emissions system. Going to look at a LMM instead. I'm curious to hear what the ultimate resolution was for your issue. Good luck.
 
#32 ·
Well the p0420 code came up as a current code today.

So today I am doing a forced regeneration myself. The grams of soot started at 44g. I now have it down to 14g. Anyone know how low I can get it?
 
#33 ·
Still dealing with the p0420 code. Nox2 ppm levels are half of nox1. Nox 1 and nox 2 percent levels are near the same most of the time. So what does this tell me?

Is there a calibration of nox sensor with a tech 2? If so how do I do it? I did see a reset but I have no clue of the procedure.

The dpf is down to 9g. The dp is .0007 when cold and .3 when warmed up. I think the dpf is clean and the 9th injector is working properly. The last 3 egts get to 1000+ during a regen.

Nox2 sensor takes a long time to respond from a cold start. I definitely have to drive the truck to get it to start showing values. Nox1 responds after a few minutes of idling.
 
#34 ·
I replaced the 9th injector. Regen temps now up to 1300 from 1100. Nox 2 levels down to 10% of nox 1. No cel after 100 miles. Still have 2 monitors to satisfy egs and dpf. Thank you for your help. Kennedy Diesel suggested this from the beginning. It may have took a while getting to it, but it was the first part that I threw at it. But really, thanks to all posting on this subject. I learned a lot.
 
#35 ·
John Kennedy Know his stuff!
 
#39 ·
I have little confidence in the ability of the truck's "on-board" computers to correctly analyze a failure, and/or suggest what parts need to be serviced or replaced.

The most recent failure was a dead truck, the code, according to the dash and my 0BDII reader, was a security code, telling me the system had suddenly decided not to recognize the key. Had to call a tow service to get the truck transported to a dealer. Their far more sophisticated "proprietory" diagnostic equipment confirmed truck had lost its prime due to a near microscopic crack in the fuel filter. Privately, they confirmed my prejudice that consumer-grade 0BDII equipment is no better at diagnostics than the on-board system. New filter housing fixed the problem.

Another totally mis-diagnostic code failure (but this one did not "kill" the truck) I was able to "clear" with my own (again, "consumer grade") 0BDII equipment - did this numerous times before giving up, taking to a dealer, where they found the 'trigger' that set off the on-board diagnostic system was the failure of my "number 6" glow plug. (total bill $187). (side note...you DONT want to do that yourself without special tools, given the risk of breaking the damn thing off inside the cyl...!)

Many problems that can result in the wrong codes, and a lot of wasted effort and costly parts, are related to the DPF, and how the on-board diagnostics react.

May I make a suggestion? In practically every city where there is any amount of OTR truck traffic, are companies that service DPF's. (for those who dont know...the DPF is the huge muffler-like device that you can only buy as one entire exhaust system...around $2,500....and since it was installed during the original manufacture of the truck before the "body drop"....you have to cut up the exhaust pipes in order to fit it into your truck...!)

The typical cost to PROPERLY service your DPF is around $800. What you get for that..is they cut the thing out of your truck...cut it apart...PROPERLY clean it ("forced regens" cant do a thorough job) weld it back into your truck, properly hook up all the sensors.

What is the typical range of a new or PROPERLY serviced DPF...? From the "jungle tom-toms" I have heard..anywhere from 80,000 miles to twice that.

Here's the bad news....if your difficulties are in fact DPF issues...sooner or later your truck will go into "limp mode", making it pretty much undriveable...dangerous if you are pulling any kind of load.

Bottom line - a PROPERLY cleaned DPF may solve your problems, after which a legit GM dealer can "clear" all codes.
 
#40 ·
I have little confidence in the ability of the truck's "on-board" computers to correctly analyze a failure, and/or suggest what parts need to be serviced or replaced.

The most recent failure was a dead truck, the code, according to the dash and my 0BDII reader, was a security code, telling me the system had suddenly decided not to recognize the key. Had to call a tow service to get the truck transported to a dealer. Their far more sophisticated "proprietory" diagnostic equipment confirmed truck had lost its prime due to a near microscopic crack in the fuel filter. Privately, they confirmed my prejudice that consumer-grade 0BDII equipment is no better at diagnostics than the on-board system. New filter housing fixed the problem.

Another totally mis-diagnostic code failure (but this one did not "kill" the truck) I was able to "clear" with my own (again, "consumer grade") 0BDII equipment - did this numerous times before giving up, taking to a dealer, where they found the 'trigger' that set off the on-board diagnostic system was the failure of my "number 6" glow plug. (total bill $187). (side note...you DONT want to do that yourself without special tools, given the risk of breaking the damn thing off inside the cyl...!)

Many problems that can result in the wrong codes, and a lot of wasted effort and costly parts, are related to the DPF, and how the on-board diagnostics react.

May I make a suggestion? In practically every city where there is any amount of OTR truck traffic, are companies that service DPF's. (for those who dont know...the DPF is the huge muffler-like device that you can only buy as one entire exhaust system...around $2,500....and since it was installed during the original manufacture of the truck before the "body drop"....you have to cut up the exhaust pipes in order to fit it into your truck...!)

The typical cost to PROPERLY service your DPF is around $800. What you get for that..is they cut the thing out of your truck...cut it apart...PROPERLY clean it ("forced regens" cant do a thorough job) weld it back into your truck, properly hook up all the sensors.

What is the typical range of a new or PROPERLY serviced DPF...? From the "jungle tom-toms" I have heard..anywhere from 80,000 miles to twice that.

Here's the bad news....if your difficulties are in fact DPF issues...sooner or later your truck will go into "limp mode", making it pretty much undriveable...dangerous if you are pulling any kind of load.

Bottom line - a PROPERLY cleaned DPF may solve your problems, after which a legit GM dealer can "clear" all codes.
I appreciate your feed back as I am planning a trip of 250 miles to get some stuff done to the truck. I just wanted to confirm that I should be good. Thank you,
Chris
If you are not having any performance issues, 300 miles shouldn't be a problem. Like you said 1200 miles on my trip did not cause my DPF to totally clog up. My regens were more frequent so the fuel economy went down, but I made it home. If you have someone with a scan tool with mode 6 data, you can watch egt sensor values. If you don't see the rear egt sensor get up to 1300 or so, your 9th injector may be bad. I helped a few friends with this same issue. Kennedy Diesel was my lead on this. Either way, I drove 1200 miles and was able to do 2 forced regens to get my DPF back to under 10%. 30,000 miles later and it still regens normal. I hate the technology on our trucks, but unfortunately it is here to stay. Tech2 tool is what I used for the forced regen. It has lots of other function as well. $250 tool 2 years ago, no idea what it cost now.
 
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