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Duramax Second Generation: 2004.5-2005 (LLY) Discuss the second generation (2004.5-2005 LLY) of the 6.6L Duramax diesel engine & associated components. 2006 LLY engine discussion belongs in Third Generation forum due to the differences of the 2006 LLY and the 2004.5-2005 LLY. Engine related discussion ONLY.

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Old 11-14-2005, 11:16 PM   #1 (permalink)
briano
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Frequently Asked Questions - FAQ - NEWBIES READ THIS FIRST

Before you read the FAQ it is recommended that you read your truck manual and diesel supplement cover-to-cover as most of your questions can be answered there. Part numbers for fuel filters, oil filters, air filters, etc can be found there along with capacities for oil and antifreeze.


Be sure and give us some feedback if this helps you or not. Corrections/additions as well.

How do I reset FUEL FILTER LIFE display? This message will appear when a reset is performed either by using the steering wheel controls or the following manual procedure. For vehicles with steering wheel controls, press and hold the select button for five seconds while the FUEL FILTER LIFE message is displayed. This message will appear on the DIC for ten seconds. For vehicles without steering wheel controls, do the following: Without pressing the pedals, turn the ignition key to the on position without starting the engine. Wait five seconds.
Completely press the brake and the accelerator pedals simultaneously and hold for ten seconds. The system is now reset.
Turn the ignition key off. The next time the engine is started, the message will no longer be displayed. Always reset the FUEL FILTER LIFE system after a fuel filter change.

How do I reset the CHANGE OIL LIGHT
Turn key on and press gas pedal 3 times within 5 seconds to reset light.

What is Turbo Bark? The easiest explanation of this is when you really floor it and build boost then suddenly let off the pedal. The result is a deep coughing sound from the engine bay. Not all Duramax's do this, but a good number do- some stock and others when a tuner is added. Whats happening is the boost pressure is built up and then has no where to go except back to the turbo. This compressed air hits the turbine and stops it in its tracks making it want to go in reverse thus producing the cough sound. Repeated occurances could hurt the longevity of your turbo. There are several threads explaining this in detail and also ways to correct and/or suppress it. The easiest way is to click on search and type in Turbo Bark. Click here for one of those search results

WHAT IS BURSTING? Bursting happens when the fuel supplied doesn't meet the demand by the computer. It will kinda "lay-down". Basically you are meeting the limits of your factory fuel system and you'll need a lift pump to increase fuel demand brought on from tuners, bigger/modded turbos, and anything that increases boost.

What additive should I use? There are several on the market and can be found with a search. GM has approved a few for use in the Duramax and one of them is Stanadyne.

When should I change oil? Fuel filter? Tranny filter? etc? Duramax Maintenance Schedule

What engine do I have? Check the 8th digit of your VIN number- LB7=1, LLY=2, LBZ=D

What tuner should I get? Tuner will vary. Figure out your needs then browse through the Electronics section for brands, pros and cons of each. Here are the most popular.

What is limping? Read about it here and to get going after limping turn your truck off for a few minutes and restart. Keep in mind once you limp the tranny it may happen more frequent. You are basically making more power than the stock tranny can handle. Typically this will appear as the engine not going over 2000 rpm's, or staying in one gear the entire time.

Where is my glow plug light? check your manual for description and location. The LLY glow plug system is revised and heats up very quickly. You may not even see the light all day except first thing in the morning.

When do I change my fuel filter? GM recommends changing it every 15,000, however a majority of owners change it more frequently. Depending on where you live and the quality of diesel fuel you may do it soon or later than most.

How do I change my fuel filter? There is a great write up in the Do It Yourself section, click here to read it.

How many quarts of oil does my truck hold? This sort of info is in the manual that came with your truck. Most Duramax’s take 10 quarts with filter.

What kind of oil should I use? Check your manual for the exact specifications you will need. This comes down to preference as many different brands are used among owners. Try a search for type of oil or related. There are many to choose from.

Which cold air intake is best? None really. It has been proven that the stock air box and paper filter actually flow the same if not better and also traps more dirt than most after market CAI out there. Most want a CAI just for the turbo whistle.

Which exhaust is best? There are many brands available, browse through the Exhaust section for names, pros and cons of each. The most widely used vendor is MBRP. Click here for the most popular ones around.

What is the maximum EGT that a Duramax can handle? Driving day to day you may see some spikes of 1200-1600 in a very short period of time. What you don't want to see are those high temps sustained for a long period of time. 1350 degrees or so is about the hightest pre-turbo temp you want your truck to get. Any higher for long periods and you risk damage to engine and/or turbo.

What is an EGR blocker plate? Click here for an explanation.

What is a finger stick? Click here for explanation

What is a Boost Stick? Click here for explanation

What is a turbo back vs. cat back exhaust? On a Duramax a turbo back exhaust kit includes the front most pipe (cat delete) that connects to the turbo down pipe, mid pipe, muffler and tips. A Cat back system is just the muffler and tips not including the cat pipe up front- basically everything from the 4 bolt flange and back.


What temp decrease will I see with full exhaust replacement? A full 4” exhaust system will drop your temps approximately 200 degrees. Some have seen less, some have seen more. The 5” systems show no real gain or loss compared to a 4”, but some report them being louder.

There is a tone change from my exhaust at idle, what is it? This is normal, it's your egr and turbo searching for idle. The veins open and close giving a rumble tone for a few seconds, then a hissing tone the next, and they cycle through. Perfectly normal for the LLY and above trucks with the electronic turbos.

Can I install an exhaust system myself with normal hand tools? Yes. The duramax exhaust has one band clamp up front and 4 bolts connecting the front pipe to the cat back. The rest of it is held by hangers. The hanger on the front pipe should be removed from the side of the tranny and the OEM front pipe w/cat will slide out the front. The rear section can be removed without cutting, however if you want to save yourself an hour of moving, jacking, lifting, etc just get a "sawz all" and cut the pipe just after the muffler and 5 minutes later you are installing your new system. Depending on what kit you decide to go with it may or may not be custom fit so you may have to cut.

What kind of mileage will I see? This is one of the most commonly asked questions on DP. Some get 11, some get 20...it varies with altitude, fuel, load, and weight of your foot. Generally the best mileage can be had by keeping rpm’s below 2000. Tuners are also known to increase mileage 1-2mpg.

When does the engine break in? This is another common question with mixed opinions. Some say the motor will break in after 10k miles. GM recommends not towing for at least 500 miles, but most wait until a 1000.

I limped my truck, how do I get back on the road? You can temporarily get out of this by shutting your motor off for 5 minutes and restarting. It’s recommended you see the dealer if this has happened.

There is a jet engine sound coming from the engine at times, what is it? This is a common question as well. The sound you hear is the clutch fan. You may hear this while towing or with the A/C turned on. Some hear this during normal driving. It’s nothing to worry about unless your engine temps seem to be higher than normal. If this is the case go to the dealer.

Do I need gauges with a tuner? Once you start adding power to a diesel let alone a turbo charged engine it is critical to know what is going on under the hood. It is strongly recommended by most power adder/tuner manufacturers that you have an EGT gauge and boost gauge.

What is the highest program you can run with the stock transmission? 90hp is about the most additional power the stock tranny can handle without needing upgrade. Running any higher tunes then you risk burning up your tranny, use at your own risk. The tuner manufacturers have warnings in place for each one of how high you can run on the stock tranny. Please read all documentation first.

I installed bigger tires and my Speedo is off, how do I correct this? At this time its not clear if the dealer can reprogram for bigger tires or not. The only other way is to purchase a tuner and get some power added as a bonus. Hypertech, Predator, TTS are just some of the ones that can change the Speedo while adding power...


What PCM updates do I have on my truck? You can go to This One. This will show what updates are available, but you will have to take the truck to the dealer to verify you have the latest and greatest using their TechII system. Make sure your pop up blocker on your browser is disabled or you will not get far.

I have this code, what does it mean? Go here for DTC codes.

What are green keys? These are replacement torsion bar parts that increase the front ride height of your truck. You can crank the stock keys to an extent, but if you want to go any higher you will need the Green keys


Do I need an alignment after I crank the T-bars? Yes. It is recommended to have this done after changing the torsion bar height.

How do I install an EGT probe? There are a few write ups in the Do It Yourself section. Edge actually has a nice write up on their site as well, click here to view it. With proper tools and some patience it can be done in 30 minutes.

What are some signs of bad injectors? Some signs are white smoke at idle, smell of raw fuel through exhaust, mileage drastically dropped, loss of power. These are just a few.

Should I remove my tuner/programmer before going to the dealer? YES. There are more non-mod friend dealers than there are friendly ones. Most will deny work once they speculate or find something installed that is aftermarket. So just to be safe remove all programmers and return to stock form for dealer trips.

I added a tuner to my truck and my DIC mileage is off, why? All tuners will throw this reading off. The only way to get accurate mileage is to do a hand calculation. Divide how many miles you drove by how many gallons you added. Tire size effects it too. 265 on a 2500 give 4% more miles and 285 give 8% more miles IIRC.

I notice my LLY has very low oil pressure, is this normal? Yes. The LB7’s had higher readings and the new LLY’s actually read low, but this is very normal for these motors.

My truck won’t go over 98 mph, what’s wrong? This is the electronic governor that we all have. You can disable this with the addition of most tuners and this will depend on the year of your truck.

Why do people replace the stock shocks with Bilstein or Rancho? The stock shocks are ok, but most report having too much of a floating feeling on the highway and on bumpy roads the rear end does not stay planted and swings out of control. Braking is highly effected with a sloppy suspension. Upgrading to Bilstein or Rancho will give you a somewhat stiffer ride and tons more control driving and stopping. This is especially critical while towing.

How do I hook up manual high idle? Click here for details

How do I enable the factory high idle option? This is detailed in your Diesel supplement that you should have read cover to cover first, however if you purchased used and don't have one then here are the instructions right from the manual. Click here to read it

What does TAP stand for? Target Applied Pressure and has to do with the TCM and Allison.



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Duramax Engine Pics, Front Pipe vs. Down Pipe Which Engine do I have?? Programmer Comparison Dual Electric Fan Install Online Manuals MBRP Powertube Install and Dyno "True" Downpipe Install

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Old 06-06-2006, 10:24 PM   #2 (permalink)
briano
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updated.

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14 LML 2500HD CC 4x4 - New
04.5 LLY 2500HD
- Sold.

LLY FAQ, Most Popular Tuner, Most Popular Exhaust, How to Search, Front Pipe Install,
Duramax Engine Pics, Front Pipe vs. Down Pipe Which Engine do I have?? Programmer Comparison Dual Electric Fan Install Online Manuals MBRP Powertube Install and Dyno "True" Downpipe Install

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