2013 Duramax LML DTC P0420

[FireCapt651]

Greetings Everyone,

I am returning here after being away for so long I couldn't even remember my old user name! Oh well - I think I'll live!

My trouble is with my 2013 Silverado 2500HD 4x4 (56k miles) with the LML Duramax triggering a DTC P0420. My dealer is not being very cooperative, essentially because they have only one diesel tech and he is, well, "cranky".

My contention is that this code is being set due to a failing indirect fuel injector (a.k.a. - the "9th injector") mainly because I can tell that for the first 5-10 minutes of steady driving it will try to regen but fail, after which the MIL comes on. I can tell it is trying to regen because the mpg will fall to 13, but when the regen fails and returns to normal operation the mpg climbs back to 23. This won't last - when the DPF fills up the truck will go into limp mode.

The dealer is saying that they won't do the work to replace the indirect injector (under the special extended warranty) because the P0420 code does not specifically state the indirect injector is bad. When I ask which code must be set before they WILL do the work they cannot answer because the TSB for this problem doesn't specify the code. Instead they want replace the catalytic converters to the tune of several thousands of dollars that I will have to pay myself and will not guarantee that will solve the problem - and I refuse to to throw new parts at it until something finally works without knowing what was wrong to begin with. That can get too expensive for me quickly.

So I guess my question is this: Is the P0420 directly indicative of a failing indirect injector, and where can I find official info from GM saying such?

Thanks for any and all help - Jon (FireCapt651)

[Kennedy]

This code is as you stated most often related to the indirect injector. I can fix most issues with programming changes, but the indirect injector and temp sensors must function. You may be better off to buy one and the release tool and change yourself or try a different dealer.

My Tech tip on the regen and this issue: http://www.kennedydiesel.com/docs/LML%20Duramax%20DPF%20Regeneration.pdf

[FireCapt651]

Thanks for all who looked at my post and for the reply I received. As an update, the technician at my dealer has had my truck for over two weeks now and I received a call yesterday saying that he finally broke down and tested - and replaced - the indirect injector. Big surprise - it's what I've been saying from the beginning. Fortunately for me it is covered under a special extended warranty from GM so there should be no money out of my pocket, just my time for the truck to be out of service at the shop.

At the start of this entire saga the service writer told me the tech claimed that the P0420 code was not the one that a failing indirect injector would set. When I asked which code would be set they didn't have an answer for me. It took me all of about 10 minutes of research online to identify the most likely issue for this code but unfortunately for me there was nothing official from GM that would confirm this I could show the tech.

I realize that just about any tech would hate it when he or she has a customer who thinks they know something he doesn't, but not all of us are uneducated. A thousand years ago I majored in marine engineering and learned on marine diesels bigger than a house. While those units are only distantly related to what I have under the hood of my Silverado, I can still read a manual and follow a diagnostic flow chart. Oh well, at least my truck is fixed.

Cheers - Jon

[More Power]

Instead they want replace the catalytic converters to the tune of several thousands of dollars that I will have to pay myself and will not guarantee that will solve the problem - and I refuse to to throw new parts at it until something finally works without knowing what was wrong to begin with. That can get too expensive for me quickly.

I'd be temped to tell the service manager... "OK, replace whatever parts you think it needs, but only do them one at a time, to see whether that part fixes the problem. If it doesn't fix the problem, the dealer eats the cost of that part."

Making friends at dealerships can be hard sometimes... :(

[JohnC]

'Scuse my likely ignorance on the subject, but what's the emissions warranty?

[FireCapt651]

'Scuse my likely ignorance on the subject, but what's the emissions warranty?

For my 2013 Silverado with the LML Duramax, the emissions warranty is as follows:

3 year/36k mile bumper-to-bumper (the standard warranty)
7 year/70k miles (federally mandated but only on a very short, specific list of parts)
10 year 120k miles special extended warranty for the indirect injector and certain parts on the DEF injection system

[FireCapt651]

I'd be temped to tell the service manager... "OK, replace whatever parts you think it needs, but only do them one at a time, to see whether that part fixes the problem. If it doesn't fix the problem, the dealer eats the cost of that part."

Making friends at dealerships can be hard sometimes... :(

I doubt you will be able to find a dealer who will agree with that. Also, I am not the type to just keep throwing new parts at a problem until the problem disappears - I want to absolutely know what is wrong (and hopefully what caused it so I can look out for it and prevent it from recurring in the future).

[More Power]

I doubt you will be able to find a dealer who will agree with that. Also, I am not the type to just keep throwing new parts at a problem until the problem disappears - I want to absolutely know what is wrong (and hopefully what caused it so I can look out for it and prevent it from recurring in the future).

I agree...

I remember a conversation I had with a diesel Suburban owner about 19 years ago, who had taken his great running Sub in for a simple fuel filter replacement.

That service visit turned out to be a $12,000 nightmare, when the idiot mechanics made the worst possible decision on just about everything... We're talking a couple new pistons, new batteries/cables, new starter, new fuel injection system and a long list of other incidentals. Long story short, they air-locked the fuel injection system, ruined the starter from cranking, hydro-locked the engine by pouring way too much fuel down the intake resulting in broken pistons, melted the batteries, and on and on. The shop tried to get him to pay for it all. He didn't. He got a good attorney.

[rapidoxidationman]

I agree...

I remember a conversation I had with a diesel Suburban owner about 19 years ago, who had taken his great running Sub in for a simple fuel filter replacement.

That service visit turned out to be a $12,000 nightmare, when the idiot mechanics made the worst possible decision on just about everything... We're talking a couple new pistons, new batteries/cables, new starter, new fuel injection system and a long list of other incidentals. Long story short, they air-locked the fuel injection system, ruined the starter from cranking, hydro-locked the engine by pouring way too much fuel down the intake resulting in broken pistons, melted the batteries, and on and on. The shop tried to get him to pay for it all. He didn't. He got a good attorney.

And this
right here
is why I'm glad this forum exists!
Letting other folks wrench on my truck (or car, or motorcycle, or lawn mower) gives me the heebie-jeebies.