Duramax FAQ

Duramax FAQ's:

Should I use fuel treatments?
Will Ultra-Low Sulfur fuel reduce the life of my fuel injectors and pump?
Why do I need low-ash oil for the LMM Duramax?
Should I install a secondary fuel filter?
Is there a special warranty on fuel injectors?
How can I prevent my LLY Duramax engine from overheating?
My Duramax goes into “limp mode” all the time. What's wrong?
What's the most effective modification that I can do to improve the performance of my Duramax?
Will aftermarket power programmers/chips affect my warranty?
Will an aftermarket exhaust cause Diagnostic Trouble Codes?

Should I use fuel treatments?
Fuel additive manufacturers offer improved protection against water, better lubricity, cetane levels, cleaning ability and fuel economy. Duramax engineers have identified one failing to look out for: water emulsifiers. In short, water emulsifiers, (generally various forms of alcohol) cause water to be suspended in the fuel. This can allow the water to actually penetrate the fuel filter/separator and cause damage.
Recommended fuel treatments: Racor Power Shot Plus and Stanadyne fuel additives

Will Ultra-Low Sulfur fuel reduce the life of my fuel injectors and pump?
Duramax fuel system was engineered for this fuel and will live a long life under normal conditions.
Why do I need low-ash oil for the LMM Duramax?
GM says that most DPF's should run about 100,000 miles (160,000 kilometers) before they will require the ash loading to be cleaned. In order to make sure that the DPF gets as much life as possible, low-ash oil was developed. You can run non low-ash oil for one oil change if nothing else is available, it will not reduce the life of your DPF that much. But you wouldn't want to run non low-ash oils for the life of your engine.
Should I install a secondary fuel filter?
GM has a very good fuel filter. It went through several improvements. On my truck, I use only the AC Delco filter and I don't have a pre-filter. You may wish to run another filter if your fuel quality is questionable, it doesn't hurt. 10 microns is sufficient, although finer filters will run with no problem as long as they are large engough to not present a restriction in the fuel system.
Just remember: change your fuel filter every 15,000 miles! (24,000 kms)
Is there a special warranty on fuel injectors?
Yes, on certain years of trucks and only with a very specific type of failure. This special warranty covers “high return rate” failures. GM responded to customer concerns to set up a “Special Policy” for this specific failure. Ball seat erosion, fuel injector body cracks and high-pressure seal extrusion are covered for a period of 7 years or 200,000 miles (320,000 kms), whichever comes first.
How can I prevent my LLY Duramax engine from overheating?
The overheat condition most often affects trucks pulling heavy loads on hot days.
GM does have a potential solution for this problem. GM provides some seals and baffles and the cold-air intake off of the LBZ diesels. This cold-air intake allows the turbo to be taking in outside air charge, instead of the heated underhood air off of the intercooler and radiator. This helps, but may not solve a persistent problem. Another improvement that GM does not indicate in the bulletin will really help: Retrofit the LBZ turbocharger inlet duct onto the LLY. The LLY inlet duct is very restrictive, and negatively impacts the efficiency of the turbocharger, causing high turbocharger outlet temperatures as well as high drive pressures for the turbo itself. With the complete air intake system from an LBZ, this problem can be largely resolved.
My Duramax goes into “limp mode” all the time. What's wrong?
There are quite a number of factors that will cause the Duramax to go into limp mode. A DTC setting in just about any system can cause a limp mode result.
Here are some common “limp mode” causes:
1. A plugged fuel filter. This will usually cause a P0093 or P1093 DTC. (depending on the model year) The limp mode will be evident after 10 seconds of pulling or accelerating hard, although if it's really plugged it can cause a limp mode with less fuel demand.
2. An injector terminal fretting problem. This is common on 04-05 LLY engines and generally affects #2 and #7 cylinders although it can affect others. It will set a number of DTC's. There is an updated 90 degree connector and support brackets for these two injectors that repairs this problem. When it goes into limp mode, the truck will barely crawl and the engine may or may not start. It also will have a loud injector rattle.
3. A leaking-down fuel injector. This will usually set a P0093 or P1093 (as above) and may manifest itself by being hard-starting or long-cranking. A number of other concerns can cause a P0093 or P1093 DTC, so it will require some diagnostics at the dealer to narrow down. The limp mode generally will manifest itself with higher fuel demands, similar to a plugged fuel filter.

What's the most effective modification that I can do to improve the performance of my Duramax?
Really, the most bang for the buck comes from a power programming. A custom program gives you exactly what you need for your combination. It is the safest and most effective way of gaining more power. Custom tuning provides the largest gains in power and fuel economy of any modification. Running really big power levels does require some gauges, a free-flowing exhaust and a cold-air intake.

Will aftermarket power programmers/chips affect my warranty?
Yes it sure can! Bottom line here is how the dealership will view your specific problem when you come back for any warranty work. Some dealerships take a complete “hands-off” approach to programmers and chips and will refuse warranty completely. These can even go to the extreme of putting a warranty denial into the warranty tracking system that GM uses which blows away your warranty completely! Your best bet with dealerships like that is to not reveal that you have any aftermarket modifications at all. On the other hand, some dealerships will take into account that you have a programmer or chip and treat each problem case by case. An exception to this is when there is a powertrain hard-part failure. GM specifically wants the dealers to check for evidence of a power program whenever they deal with a hard part failure.

Will an aftermarket exhaust cause Diagnostic Trouble Codes?
Generally, any exhaust system that improves flow appreciably will change the expected flows during EGR operation. That can cause Diagnostic Trouble Codes (DTC) to set and possibly turn on the Malfunction Indicator Lamp (MIL.) And that all depends on the generation and emissions level of Duramax that you are running. With the LB7's, LLY's and LBZ's I can program out the EGR system completely and you will never set another EGR DTC again!