P1093 Engine Code – Chevy Duramax LLY – Diagnosing & How to Fix it

P1093 code means low fuel rail pressure during enrichment. In layman’s terms, it means the motor is not getting enough fuel. 

The p1093 code for the Duramax engine is typically found between the year 1999-2007 classic Chevy 2500 with a Duramax motor.

Symptoms of these problems include the following: 

  • Hard start
  • No start 
  • Rough idle 
  • Bogging down during acceleration 
  • A knocking sound (called a fuel knock) 
  • White smoke from the exhaust 
  • Loss of power 
  • Engine code 

Common causes for p1093 include the following: 

  • Clogged fuel filter 
  • Air in the fuel system 
  • Leaking fuel injectors 
  • Fuel injector stiction 
  • Faulty or broken fuel pump
  • Faulty or broken fuel rail sensor 
  • Water in the fuel system 
  • Faulty computer engine programming 
  • Clogged fuel injector nozzle or nozzles 
  • Broken or faulty fuel injectors or injectors 
  • Shorted fuel injector wiring 

Common fixes for p1093 engine code in Duramax 

  • Priming the fuel system 
  • Replacing fuel injector nozzle or nozzles 
  • Using diesel adaptive to clear injector stiction 
  • Draining fuel water separator 
  • Replacing diesel within a tank
  • Checking engine computer injector timing and spray patterns 
  • Checking injector rail for clogged and clearing them 
  • Checking injector wiring for shorts and repairing them 

As you can see there are many different causes and symptoms for this error code. I will go through different methods of repair from personal experience. By no means am I a professional Duramax engine repairman. But I have had my fair share of all-nighters diagnosing my LBZ…

Well my LBZ, LLY, 12v, 24v, common rail, 6.0 power stroke, and 7.3l IDI. I’ve been through a couple of trucks over the years. All with their issues – including the p1093 error code on my LLY. Many diesel trucks have fuel injection issues – it’s just as one would say nature of the beast.  

These Diesel engines run entirely off of compression and require a high-pressure mist of diesel fuel to keep the ignition going. There is not a spark plug that ignites the fuel every time its fuel enters the cylinder.   

Instead, the glow plugs of the engine will warm the fuel prior to the engine starting. This will help the fuel reach a temperature closer to that of igniting. During the compression stroke of the engine, the air is compressed in a way to produces high amounts of heat. Diesel fuel is introduced to the cylinder and instantaneously ignites. 

This cycle is repeated thousands of revolutions per minute. (RPM) it’s a fine line between compression, forced induction, and fueling to create that reliable torque power we enthusiasts seek. 

Fixing a clogged fuel filter on a Duramax: 

The fuel filter location is different on different engine styles of the Duramax. On the LLY Duramax model, the fuel filter is typically located on the passenger side of the engine next to the exhaust header. Keep in mind many people relocate the fuel filter further away from the engine to help keep the diesel cool. 

  1. Unscrew the fuel filter 
  2. Find a quality replacement filter 
  3. Fill the filter up to the very top 
  4. Rub some diesel on the o ring 
  5. Install new full fuel filter 
  6. Empty the fuel water separator 
  7. On top of the fuel filter housing open the relief valve 
  8. Cycle the fuel pump with the key in the ignition (you do not need to turn the engine over to do this) 
  9. Once fuel exits the relief valve closet it 
  10. Start truck 

If you have an engine code scanner, plug it in and clear all engine codes. See how it rides – after 30 miles if the code hasn’t reappeared, it has been fixed. If the code comes back try these other repairs below. 

Air in the fuel lines on a Duramax 

Sometimes when injector lines crack, or rubber fuel hoses dry rot, you will begin to have air enter the fuel system. This causes havoc because air and liquids do not mix. They will fight each other until the end. Sometimes resulting in ruptured injection lines. 

It is extremely important if you are getting a p1093 engine code that you inspect all fuel lines for:

  • Cracks
  • Missing or broken rubber seals
  • Pinholes 
  • Dry rot 

Even the smallest pinholes can introduce enough air to hydro-lock your fuel system. 

Fuel injector stiction 

Stiction is caused by the build-up of oils from the diesel inside the injector itself and the oil from the high-pressure oil pump that runs the injector. The oil is under such immense stress it will begin to break down on the molecular level. The fluid property of the oil will become more of that of sludge. 

Due to the extremely high pressures diesel is misted from out of the injector, even the smallest amount of build-up can reduce fuel causing p1093 engine code.  

This stiction can build up within the spool, o rings, nozzle, and even in the turbocharger.  

I struggled with stiction on my 04 6.0 power stroke I had. I ended up using what Power Stroke Ingenuities suggested, which is called AR6400-D Diesel Fuel Additive system cleaner. It helped a good amount, it was very expensive; about $20 per treatment. The injectors need 5-6 treatments. To clarify, 1 treatment per gas tank full of diesel. This can take a while to see results.  

The other option is nuclear, but it may be what you decide. Go buy new injectors – yea crazy right! Injectors are $400 a pop right now. Sometimes pushing over to 600-1000 a pop if you want more fuel than stock. But here’s the thing. You probably do not need to do all the injectors. Take it to a local diesel shop and have them either bench test the injector or set up a computer. They will be able to tell you which injectors need help. 

Leaking injectors on a Duramax engine 

Leaking injectors is common. The largest contribution is from broken or dry rotted o rings that help seal the injector in place. Take a look at this, if you find a problem nozzle and o-rings sets are sold for a reasonable price. 

Faulty or broken fuel pump on a Duramax 

The easiest way I have found to test a fuel pump on almost any vehicle is to just pull a line off the rack. Throw it in a milk jug and then cycle the fuel pump from the ignition (again I’m not cycling the engine, just the fuel pump). 

If nothing comes out, then I’d replace the fuel pump. If the flow is strong I would re-install the line, re-prime the injectors and look elsewhere for a solution. 

Faulty or broken fuel rail sensor on a Duramax 

I know, at least on an LLY, the fuel rail sensor is in between the driver-side valve cover and the intake manifold. This part is extremely easy to find, replace, and inexpensive. Just slap a new one in if you are already there.  

Genuine OEM Part – 0281002851

OE# 97361561 0281006325

Once replaced – you can clear the engine codes once again. After 30 miles and no check engine light for code 1093. You’re in the clear!

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