Chevy and GMC Duramax Diesel Forum - Reply to Topic
11-16 LML Duramax Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission, Etc.

Thread: 2014 lml p0420 code Reply to Thread
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  Topic Review (Newest First)
02-16-2020 03:48 PM
Los1wing 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.
01-21-2020 10:36 AM
Los1wing 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?
12-29-2019 09:13 AM
Los1wing
Quote:
Originally Posted by poosniffer View Post
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.
No more pending codes. I still have the perm code p0420. I need another trip or two to hopefully clear it.
12-29-2019 03:20 AM
poosniffer 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.
12-19-2019 06:37 AM
Los1wing 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 .
12-13-2019 06:03 AM
Los1wing 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?
12-12-2019 02:10 PM
Los1wing 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.
12-12-2019 01:39 PM
redwngr
Quote:
Originally Posted by Los1wing View Post
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.
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.
12-12-2019 12:58 PM
Los1wing 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.
12-04-2019 05:06 AM
Los1wing 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.
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