Exhaust Aftertreatment Systems Services & Repair

717-738-2461 (Ephrata, PA) | 717-656-2366 (Leola, PA)

Exhaust Aftertreatment Systems Service and Repair
EGR – Exhaust Gas Recirculation Cooler VGT (Variable Geometry Turbocharger) EGR (Exhaust Gas Recirculation) Value Inlet and Outlet NOx (Nitrogen Oxide) Sensors Exhaust System Sensors DOC (Diesel Oxidation Catalyst) DPF (Diesel Particulate Filter) SCR (Selective Catalyst Reduction) Catalyst DEF (Diesel Exhaust Fluid) Tank DEF (Diesel Exhaust Fluid) Pump Module Inlet and Outlet NOx (Nitrogen Oxide) Sensors

Click on the numbers or scroll down for more information about the PARTS involved in this process.

Parts

The exhaust aftertreatment system requires proper functioning of many different components.  Here’s a simplified explanation of many of the parts involved in this process.

AfterTreatment Systems Service and Repair

View the list of parts below
(scroll side to side).

Specialized Expertise and Cutting Edge Capabilities

A truck’s exhaust aftertreatment system is complex. Its performance affects—and is affected by—other vital systems within the vehicle. If it doesn’t get the attention it needs, you run the risk of unanticipated downtime, decreased fuel efficiency, and extra costs.

Exhaust Aftertreatment System Sensors
Sensors at work capturing readings as exhaust exits the after-treatment system.

At GSFA, we have the specialized expertise and technology to service and repair systems by all of the top truck manufacturers. Our fully trained technicians have an in-depth understanding of each exhaust aftertreatment system, and we have the electronic systems in place to update your vehicle’s software when new releases are launched.

Exhaust Aftertreatment System 1 pc design from Cummins
As system technologies evolve, configurations will change & improve to be more application specific. Here is an example of a current 1-pc design from Cummins.

Skilled Service Backed by Direct Support from Manufacturers

Few shops have the same level of diagnostic and service capabilities as GSFA. Moreover, with our strong relationships with OEMs, we can even tackle tough-to-diagnose, persistent issues that other truck garage’s may find difficult to resolve.

Exhaust Aftertreatment System Sensors
Exhaust Aftertreatment System 1 pc design from Cummins

Sensors at work capturing readings as exhaust exits the after-treatment system.

As system technologies evolve, configurations will change & improve to be more application specific. Here is an example of a current 1-pc design from Cummins.

Parts

The exhaust aftertreatment system requires proper functioning of many different components.
Here’s a simplified explanation of many of the parts involved in this process.

(Click on a part to show the part within the system.)

1. EGR – Exhaust Gas Recirculation Cooler The EGR is a heat exchange unit that uses engine coolant to lower exhaust gas temperature as it leaves the engine. As exhaust flows through tubes of engine coolant, its temperature is decreased so that it can be processed and recirculated back into the engine.Back to top
2. VGT (Variable Geometry Turbocharger) A turbocharger that gives the engine an on-demand way to control the amounts of backpressure, boost, and exhaust temperature it creates to meet the load conditions or the aftertreatment requirements of the engine. Back to top
3. EGR (Exhaust Gas Recirculation) Value An electronically controlled valve that regulates the amount of exhaust gas that flows back into the engine. Unused exhaust gas gets passed through the VGT and removed. The EGR allows the engine to lower NOx internally by lowering cylinder temperature.Back to top
4. Inlet and Outlet NOx (Nitrogen Oxide) Sensors These smart sensors provide instantaneous data back to the control module that measures the NOx level before and after exhaust gas is treated. The control module uses the data to determine the amount of diesel exhaust fluid (DEF) that needs to be injected into the exhaust stream.Back to top
5. Exhaust System Sensors These sensors send information about ammonia content, oxygen content, temperature, pressure, exhaust flow, and other metrics to the control module.Back to top
6. DOC (Diesel Oxidation Catalyst) This aftertreatment device initiates a chemical reaction using unburned fuel, oxygen, and heat to start the regeneration process.Back to top
7. DPF (Diesel Particulate Filter) As exhaust gas flows through this filter, it traps and collects soot. When the soot load reaches a predetermined level, regeneration is needed. During regeneration, the soot turns to ash, which eventually needs to be removed from the filter.Back to top
8. SCR (Selective Catalyst Reduction) Catalyst This component uses heat, exhaust, and diesel exhaust fluid to create a chemical reaction that alters the state of the exhaust gas. It removes NOx from the exhaust and turns it into water vapor.Back to top
9. DEF (Diesel Exhaust Fluid) Tank This sealed unit serves as a holding tank for diesel exhaust fluid. Typically, it is black in color for protection against ultraviolet rays and has a blue cap.Back to top
10. DEF (Diesel Exhaust Fluid) Pump Module This component filters the DEF and distributes it to the DEF doser during engine/vehicle operation. When the unit shuts down, it reverts DEF back to the tank to clear the supply line. If you hear buzzing after you turn your truck’s ignition off, it might be the revert process in progress. This reverting process may take up to two minutes. During this time, it is very important that power is not disrupted because damage to the system can occur. If using battery disconnects on newer units, it is a good practice to allow five minutes after “key off” before switching the disconnect to the off position.Back to top

Process

As manufacturers try to adhere to the strict guidelines set forth by the EPA, many new technologies, as well as challenges, have been introduced.  As part of this evolution, we have become familiar with the term “DPF” which stands for Diesel Particulate Filter. This is one of the main components in a multi-stage system that collects unwanted soot and reduces it to ash through a process called “regeneration,” commonly referred to as “regen.”

General steps for what happens and what parts are involved leading up to and during an automatic regen:

Step 1
The truck’s engine takes in clean air to use for combustion. At same time, the control module meters exhaust gases to recirculate air back into the engine.
Step 2
Combustion gas is expelled out of engine through the exhaust manifold, where it gets split two ways between the variable geometry turbo (VGT) and the exhaust gas recirculation (EGR) valve and cooler.
Step 3
Exhaust gas is constantly monitored for temperature, pressure, NOx content, flow, and various other parameters. Sensors report that data back to the control module.
Step 4
If the control module identifies a regen is necessary, the VGT can change positions to control airflow through the turbine and increase temperature to initiate the regen sequence.
Step 5
Once a predetermined diesel oxidation catalyst (DOC) inlet temperature is reached, fuel is dosed into the exhaust stream either through an external doser or the engine’s electronic injectors.
Step 6
The combination of heat, unburned fuel, and unused oxygen in the exhaust become chemically transformed as they pass through the media in the DOC.
Step 7
The resulting chemical reaction causes the DPF temperature to increase and burn the soot trapped in the DPF, turning it into ash. The ash collects there until the unit is serviced. (The typical DPF service interval to remove the ash is every 250,000 miles or 500 hours.)
Step 8
As the exhaust gases continue to flow through the DPF (with soot no longer an obstacle) diesel exhaust fluid (DEF) gets injected into the stream before it enters the SCR (selective catalyst reduction) catalyst.
Step 9
As exhaust passes through the SCR catalyst, another chemical reaction occurs to remove NOx and turn it into water vapor.
Step 10
The remaining gases exit the tailpipe or stack.

If an automatic regeneration fails to take place, regen can alternatively happen through:

  • Driver-initiated regeneration when the driver responds to the Diesel Particulate Filter Regeneration Lamp warning light
  • Mechanic-initiated regeneration with an electronic service tool

If regeneration has not been completed, and the unit reaches a critical state, the DPF will need to be removed and professionally cleaned or replaced.

Exhaust system warning lamps to be aware of:

Diesel Particulate Filter Regeneration Lamp

Diesel Particulate Filter Regeneration Lamp

Indicates that regeneration is required, and conditions were not met in order to complete an automatic regeneration. May require increasing the load on the engine or doing a stationary regen when the vehicle is parked.

High Exhaust System Temperature Lamp

High Exhaust System Temperature Lamp

Indicates that the vehicle speed is less than 5 mph and the DPF outlet temperature is more than approximately 840o F (450o C). This condition can occur under normal operation. No action is required.

Malfunction Indicator Light (MIL)

Malfunction Indicator Light (MIL)

Indicates that an emissions component or process has failed multiple trips and needs to be serviced.

Aftertreatment Diesel Exhaust Fluid Light

Aftertreatment Diesel Exhaust Fluid Light

Indicates that the DEF tank level is low, or there possibly is a fault within the DEF system.

Enduring Ethics and Integrity

Just as we do when providing our other services, GSFA demonstrates the highest integrity and industry best practices when working on exhaust aftertreatment systems. We in no way illicitly alter or remove systems.

Call 717-738-2461 (Ephrata) or 717-656-2366 (Leola), for more information about your vehicle’s specific exhaust aftertreatment maintenance needs and to set up a service schedule that will keep you safely and productively on the road.

For Service

EphrataLeola

For Service:

717-738-2461 (Ephrata)

717-656-2366 (Leola)

Enduring Ethics and Integrity

Just as we do when providing our other services, GSFA demonstrates the highest integrity and industry best practices when working on exhaust aftertreatment systems. We in no way illicitly alter or remove systems.

Call 717-738-2461 (Ephrata) or 717-656-2366 (Leola), for more information about your vehicle’s specific exhaust aftertreatment maintenance needs and to set up a service schedule that will keep you safely and productively on the road.

For Exhaust Aftertreatment Systems Services & Repair:

717-738-2461 (Ephrata)

717-656-2366 (Leola)