On my way to work this morning and I started feeling the truck jerk every few minutes while at highway speed.

Got into town and driving 40 it keeps doing it and it starts happening more frequently.

My dash finally lights up and it goes into limp mode. Service engine and says I need to service emission or fuel system.

Any thoughts?

Has 88k on it. Filled up with diesel yesterday and drove 125 miles after fill up.

Before I take it to the dealership or mechanic, can On Star tell me the code it is throwing?

Not sure what to do since I work 50 miles away and the dealership is the last place I want to go since it has no warranty remaining.

The Duramax diesel has a warranty of 5 years/100k miles.

Nine times out of ten, shutting off, waiting 30 seconds, and restarting will cure limp mode.

And any parts store can read your codes. You can decide what to do about it after that

I've never heard of Onstar being able to tell you the fault codes. Autozone, or any of those type places will read the code for free (usually), but you've got to get it there. I would immediately poor a bottle of diesel additive in the tank, I'm partial to to Hot Shot's Secret Diesel Extreme, but there are a bunch of them out there. You want one that increases the cetane and removes/disperses water.

I'm guessing a transmission issue wouldn't trigger limp mode right?

Bronco6Gen said:

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I would immediately poor a bottle of diesel additive in the tank, I'm partial to to Hot Shot's Secret Diesel Extreme.

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Tell me more, please. 2014 Cummins 6.7 with about 50,000 miles. Is this a once-in-a-blue-moon treatment or more frequently?

Edit: Well, guess I could've read the label first. https://www.hotshotsecret.com/signature-series-fuel-pack/

I did the On Star deal and they got me a code and everything on the diagnostics check.

P0204 is the code. Injectors most likely and hopefully since warranty will cover. Talked to a dealership finally as well.

Now I need to make it to the dealership in Cuero so I can have my wife pick me up. Have a little league game tonight as well to coach.

It's just one of those days.

That's the pigtail for the #4 cylinder, easy fix once you get to it, PITA to get to....common problem with those engines

I don't do the every tank thing. One of the concentrated bottles every 20K miles or so, or if you suspect bad diesel.

I am assuming this is not covered under warranty then?

I don't see why it wouldn't be covered.

When is the last time you cleaned the MAP sensor? Not MAF. That thing gets gummed up with soot and can affect performance. It's very easy and videos available on YouTube.

I had my F250 go into limp mode because of a bad injector in the DEF system

Would gasoline in the tank possibly cause this? Not saying the OP put gas in his truck but wondering if gas got mixed into the tank he filled up with.