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Why Won’t Your Engine Regen?

By on March 1, 2017

Basic Diagnostics You Should Know


Hardly a week rolls by without someone involving me in a conversation about an engine that won’t perform an after-treatment regeneration. The conversation is usually followed by a request to force a regen. It is critically important to know that if your engine will not regen, a defect must be identified and corrected. This article provides some much-needed information and, hopefully, clears up some misconceptions.

Before your red, check-engine light appears and your engine derates, your onboard computers have attempted many programmed routines to help clean the DPF. Your engine monitors the amount of fuel passing through it, as well as the pressure and temperature in the diesel particulate filter (DPF). A programmed calculation then determines the actual restriction or identifies the projected DPF restriction.

Your engine passively attempts to keep the DPF clean as you travel down the highway. If the DPF is not successfully cleaned, your yellow DPF light will illuminate, requiring the driver to help with the process. He has two options: change the mode in which the vehicle is being operated in order to get more heat into the exhaust, or stop and perform an active regen. If not, the red light will eventually illuminate, and the engine will shut down or derate. Of course, the best course of action is to do everything in your control to prevent this warning light from ever being activated.

Maintenance Checks

DPF problem prevention starts with basic maintenance. For example, if your fuel filter is extremely dirty, the engine may not be able to generate enough heat to regen itself or even allow you to initiate an active regen. As part of your maintenance schedule, your engine manufacturer may require a valve adjustment, sometimes referred to as running the overhead. If this is not done when recommended, your engine performance could be negatively impacted, creating a condition that prevents sufficient heat for regeneration.

Your air filter may simply be so dirty that it restricts the amount of air required for your engine to reach top performance. Also, the DPF doser, an injector located in the exhaust after the turbo, can become clogged and should be cleaned periodically. If the truck will not enter a regen cycle, the DPF doser should certainly be evaluated,

One more area of concern: be sure that the DPF system is properly sealed. Leaks can be identified by the black soot residue near sealing surfaces. Some manufacturers do not have a standard seal, but use exhaust tape. The tape must be properly applied to prevent leaks. The diagnostic checks referenced in this article are not all-inclusive, but rather provide an initial guide to identifying why your DPF system will not begin a regeneration event.

At TA-Petro, DPF cleaning services are provided in five markets: Nashville TN, Dallas TX, Chicago IL, Atlanta GA and Columbia NJ. DPF diagnostics are provided at most TA Truck Service locations from coast-to-coast and on most engine platforms. As the industry gains more experience with this clean-air technology, you’ll find certified TA Truck Service technicians ready to help you keep your truck rolling safely and on time.

Homer Hogg’s Maintenance Matters airs on the Dave Nemo Show (Road Dog Trucking, SiriusXM 146), 8 a.m. ET, the first and third Thursdays of each month.

Homer Hogg, Manager of Technical Development for TA and Petro, has worked as a truck technician for more than 35 years. He is ASE Master-Certified, a Daimler Certified Trainer, and a member of the Nashville Auto-Diesel College Hall of Fame.

About Warren Eulgen

One Comment

  1. Kevin

    April 7, 2018 at 12:41 pm

    I drive a 2016 Western star 5700xe and the last 2 months has been a nightmare, the DPF system has failed 4 times requiring a tow to the dealer.
    The dealer obvious does not have a qualified technician able to diagnose and repair DPF systems.
    The manual regen system wont work and eventually the engine shuts down.
    There needs to be more facilities able to repair these systems to prevent extended down time.
    If anyone knows of DPF specialist in the Vancouver BC area let me know.

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