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How To Replace A Diesel Exhaust Fluid Pump

When your diesel exhaust fluid (DEF) pump fails, the DEF can no longer be injected into the exhaust system. When that happens, your truck will think that it's out of DEF and then enter "degraded mode".

Some drivers assume they just need to fill up their DEF tank, but it may actually be the pump that needs replacing. Replacing this pump is necessary to ensure that your vehicle is still safe and legal to drive on public roads. Here's what you need to know about replacing a diesel exhaust fluid pump.

What Causes A Diesel Exhaust Fluid Pump To Fail?

Failing diesel exhaust fluid pump

If you are having trouble with your diesel exhaust fluid pump, there are several possible causes. Some common causes include:

  • Crystalized deposits in the pump from either overdosing or hard water top-ups
  • DEF that’s contaminated with dirt, rust, or tank scale
  • Contamination of the DEF tank with other fluids
  • Wear and tear
  • Component failure (such as wiring)

How To Replace A DEF Pump On A GM Diesel Truck Or SUV

Image Credit: LehewTech

Replacing a DEF pump is a pretty straightforward process. All you need to do is access the Selective Catalytic Reduction (SCR) system on your truck or SUV, remove the old DEF pump, and then bolt the new one in place.

Usually, the hardest part is accessing the SCR system. It can be quite difficult on some vehicles, and easy on others. For example, if you own a 2011+ Ford Super Duty truck, you would need to remove the truck bed to access the DEF pump.

The good news is GM vehicles are designed better than that. You should be able to slide underneath your truck, remove the DEF tank, and then pull out the old DEF pump. When you drop the DEF tank, you'll see the pump on top of it.

In some vehicles, the DEF pump is located within the DEF reservoir. Before starting this DIY project, it's a good idea to find out how to access the DEF pump in your particular vehicle. This way, you'll know what to expect, and you'll know which tools you'll need ahead of time.

Tips To Ensure That Your DIY Job Goes Smoothly


The SCR system in your truck or SUV is quite important for emissions. Without it, your truck or SUV won't run well. So when you access the system to replace the pump, you want to make sure that nothing goes wrong. Here are some tips to help you get the job done right:

1. Fix Any Emissions Problems Beforehand

Prior to performing this procedure, take your truck or SUV to a mechanic to have it scanned for any emissions problems. If there are emissions problems, get them fixed before replacing the pump. That way, you'll know that your vehicle can pass emissions after replacing the DEF pump.

2. Cover All The Holes

As soon as the old pump comes off, cover up any of the holes leading into the SCR system. This will prevent any dirt and debris from falling into the system and contaminating the fluid.

3. Prime The New DEF Pump

Before installing the new DEF pump, make sure to prime it first. This will ensure that the DEF flows properly through the lines. To prime your new DEF pump:

  1. With a syringe, siphon some of the DEF from the hole where the old pump was.
  2. If the DEF looks clean, inject it into the new pump. If the fluid looks dirty, it's contaminated. In that case, you need to replace the DEF before installing the new pump.
  3. Repeat these steps a couple more times until the fluid leaks out of the smaller ports on the new pump.

4. Buy An OEM Replacement Part

If you want your new DEF pump to last, get an OEM pump. OEM stands for "original equipment manufacturer". An OEM part is made by either GMC or a company hired by GMC. It's a direct replacement of the stock part on your vehicle. That means an OEM DEF pump will match up with related parts and your vehicle's electrical system.

You'll find great prices for OEM parts online. In fact, you'll find the lowest total transaction prices on our website. We're an authorized retailer of genuine OEM GM parts, and we offer low prices.

We have OEM DEF pumps for GMC and Chevrolet trucks and SUVs. This DEF pump for 2012-2016 Silverado and Sierra HD trucks is one of our best sellers. Please contact us if you need help finding the right OEM DEF pump for your vehicle.

7. Test Out The New Pump

Once the new DEF pump is in place and primed, turn on your truck or SUV's ignition. Verify that you are getting the proper DEF flow by checking your DEF tank gauge. If everything is in order, your truck or SUV should be OK to drive again.