Common Problems: DPF Turmoil

What's the deal with regen?

May 2018 Feature Colin Peterson

If you haven’t heard the term “regen” yet, you’ve probably never owned a newer diesel, nor known someone well who owns one. Many problems on trucks manufactured in 2007 or later have something to do with the components of the dreaded after-treatment system, including the diesel particulate filter (DPF) and its process of regeneration. When the US Environmental Protection Agency (EPA) implemented a new set of regulations in 2007, we said a big “goodbye” to simple exhaust systems. With the new after-treatment systems installed on trucks since then, soot gets turned into ash through the heat generated by the chemical reaction of a diesel oxidation catalyst (DOC). It’s a very disadvantageous system, as it drastically lowers fuel mileage while the ash builds up on the DPF. Through the process of regeneration, the ash gets burned off; this process must occur on a regular basis to prevent serious engine damage.

What Is Regeneration?

Regeneration isn’t a very time-consuming process, but it must be done if you want to safely keep your precious truck. When the light with the exhaust symbol goes on, it’s time to regenerate. DO NOT IGNORE IT OR PUT IT OFF! Passively, regeneration can be done through normal exhaust system heat by driving at highway speeds for a half hour or so; if you’re making a long road trip, this is very convenient, because the truck will regenerate automatically after the light goes on. When driving in the city, however, the exhaust likely won’t get hot enough for an uninterrupted regeneration. That’s when it’s time to take the truck to the shop to perform a stationary regeneration. Because of the extreme complexity of the DPF system, the regeneration process is often extremely temperamental. If the process doesn’t run to completion or doesn’t run properly, it can cause other problems that could lead to engine damage because it puts backpressure on the engine and cripples performance.

To help explain what customers should look out for on their trucks, we spoke with Master Technician Brock Carter of Broadway Ford, and service manager John Giannini, Jr. of Smith Chevrolet, the dealerships near our offices in Idaho Falls, Idaho.

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