Questions and concerns w my 15

Hey guys,

I have a few questions because this is my first duramax. I've had several fords and dodges but still figuring out the duramax.

So I bought my truck last month. After about two weeks I brought it back to the dealer to have steps installed. On the way down the display notified me that the def was low. I had the dealer top it off while it was there. They told me that it comes with only 3g. They added 4g. This was at 1000m.

Then about three weeks later I get a CEL. When I checked in w Onstar they told me it was a code for inj 1 out of learning range. The def message showed up again on the way to the dealer.

The dealer replaced the inj and added almost 5g of def. this is all within 3300m.

I'm concerned that the inj was bad at 3k but whatever.

The thing that is really bothering me is the def usage. So far I've counted about 5-6 regens since I've had the truck. The first time it regen'd I couldn't figure out what was up w it because it was idling at 850-900.

I drive in LA traffic and usually do about 100-150m a day. The reports I read and what the dealer told me was that you shouldn't need to touch the def between oil changes.

This is now about 14-16g in half an oil change. I could understand using more if I'm towing, but I haven't even towed w it yet and honestly I've been driving it like an old lady. It hasn't shifted higher than 2200 yet.

I thought that maybe the regen's and def usage was from the bad inj but it just regen'd again today and it took about 45min to complete. This is 300m after the inj was replaced.

The last thing I am questioning is fuel mileage. It seems to regen about every 500m so it's killing my mileage. The first tank I averaged about 16. Then it stayed around 15.5. The last tank was 14.5. This is all hand calculated. My 99 dodge w twins sticks and fuel would average 14-15 and it had 225k on it.

Does anybody have any ideas? I really love the truck and just want to make sure everything is cool.

Bring it back. The dealer can see requested regen cycles and completed cycles. Your truck is WAY outside the norms.

Agreed. Take it back and let them fix it

Thanks for the replies guys. I'm scheduling another appointment now. The dealer takes care of me, but I hate taking it in because I just want to drive and enjoy it.

What are realistic mileage numbers for it in mixed driving? I would expect around 16 and better on the highway.

matty169 said:

Bring it back. The dealer can see requested regen cycles and completed cycles. Your truck is WAY outside the norms.

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What are normal regen cycles? How often and how long?

Those are normal mpg numbers in mixed driving. I'm seeing 12.5mpg towing, 15.5 city driving and 17-19 on the highway.
Regen averages once in about 400-500 miles in city driving and 600-700 miles highway. Length of regen depends on the driving use while it is regening.

This is with 150hp tune though which fuels hard and has instant spool up without the dead peddle.

Your DEF usage seems very high. I have used approx. 15 gallons in 14k miles.

IdahoRob said:

Those are normal mpg numbers in mixed driving. I'm seeing 12.5mpg towing, 15.5 city driving and 17-19 on the highway.

Regen averages once in about 400-500 miles in city driving and 600-700 miles highway.



This is with 150hp tune though which fuels hard and has instant spool up without the dead peddle.



Your DEF usage seems very high. I have used approx. 15 gallons in 14k miles.

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Thanks Rob. Sounds like everything is pretty much cool except the def usage.

It seems to regen around 500-600m which sounds about the same as what you're seeing.

What tune are you using? It sounds like you still have all the emissions.

I tune many LML's but only with factory emissions intact.