Exhaust System-Overview

WARNING: This page is about a different car, the 2020 Ford F-150. However, it is still accessible from the selected car via links, so may be relevant.

DPF

WARNING: Manual regeneration of the diesel particulate filter causes the exhaust gas to get very hot, very quickly. Initiate a manual regeneration only when the vehicle is on the ground with the area around the tailpipe free of people, obstructions, foreign material or other items. Failure to follow these instructions may result in serious personal injury.

NOTE: Do not use silicone based sprays or lubricants on any components installed onto or around the diesel exhaust system or intake air distribution and filtering system. Silicone reacts with the Nitrogen Oxides (NOx) sensor and may cause permanent damage to the NOx sensor.

NOTE: For areas where ultra low sulfur diesel fuel (15 ppm sulfur maximum) is required, use only ultra low sulfur diesel fuel in diesel vehicles equipped with a Diesel Oxidation Catalytic Converter (DOC) and Diesel Particulate Filter (DPF). In a diesel vehicle that is continually misfueled by using low sulfur (16-500 ppm) or high sulfur (500 ppm or greater) diesel fuel, the sulfur can effectively poison the catalyst. Continuous use of low sulfur or high sulfur can destroy the catalyst and render the catalyst useless.

NOTE: Do not use oil or grease-based lubricants on the insulators. These lubricants may cause deterioration of the rubber. This can lead to separation of the isolator from the exhaust hanger bracket during vehicle operation.

The Diesel Particulate Filter (DPF) System consists of:

Diesel Oxidation Catalytic Converter (DOC)

Pressure Differential Sensor

Exhaust Temperature Sensors

Engine NOx sensor and module

The exhaust system provides an exit for exhaust gases and reduces engine noise by passing exhaust gases through the catalytic converters and a muffler assembly. The catalytic converters also play a major role in reducing air pollutants.

The DPF reduces the pollution generated by diesel vehicles by filtering soot and ash particles out of the exhaust gases.

The PCM monitors the pressure differential sensor, DPF temperature sensors and other inputs to control the operation of the DPF system.

Soot particles can accumulate in the post DPF exhaust tailpipe. The accumulation of the soot particles should not be considered a concern, as the DPF is not 100% efficient at filtering the soot particles.

The amount of matter trapped in the DPF is monitored using the pressure sensor which monitors the exhaust pressure before the DPF. As the DPF fills with soot, exhaust flow through it is restricted.

When this occurs the pressure differential in the exhaust before the DPF will increase which will indicate to the PCM that a DPF regeneration is required to clean it.

DPF Regeneration

WARNING: : Do not park or idle your vehicle over dry leaves, dry grass or other combustible materials. The regeneration process creates very high exhaust gas temperatures and the exhaust will radiate a considerable amount of heat during and after regeneration and after you have switched the engine off. This is a potential fire hazard.

NOTE: Avoid running out of fuel.

The diesel particulate filter on the vehicle requires periodic regeneration to maintain its correct function. This is carried out in two ways, passive regeneration and active regeneration. Both methods occur automatically and require no actions from the driver.

If the journeys meet one of the following conditions:

Drive only short distances.
Frequently switch the ignition on and off.
The journeys contain a high level of acceleration and deceleration.

It is must carry out occasional trips with the following conditions to assist the regeneration process:

Drive the vehicle in more favorable conditions, which you will find at higher vehicle speeds in normal driving, on a main road or freeway for a minimum of 20 minutes. This drive may include short stops that will not affect the regeneration process.
Avoid prolonged idling and always observe speed limits and road conditions.
Do not switch the ignition off.
Select a suitable gear to ideally maintain engine speed between 1500 and 3000 RPM.

During the regeneration process, it is possible that white smoke may be emitted from the exhaust tailpipe. This is a by-product of the regeneration process and should not be considered a concern.

During regeneration at low speed or engine idle, you may smell a hot metallic odor and could notice a clicking metallic sound. This is due to high temperatures reached during regeneration and is normal.

Changes in the engine or exhaust sound may be heard during the regeneration process.

The pressure differential sensor is connected to the DPF by the pressure differential sensor line to monitor the exhaust pressure. The pressure differential sensor converts these measurements to a signal voltage, which is then sent to the PCM. The PCM uses the pressure differential sensor information to determine whether to carry out a regeneration.

The PCM will choose the optimum time for the regeneration of the DPF. Under normal operating conditions the regeneration process occurs when the PCM has calculated that the DPF requires regeneration and that predetermined vehicle conditions are met (for example coolant temperature, vehicle speed and engine load).

During the DPF regeneration the temperature of the exhaust gas increases to greater than 550C at the DPF. At this temperature soot burns. Soot particulates that may have accumulated in the diesel particulate filter are burned and the ash is trapped in the diesel particulate filter.

The ash particulates that remain in the diesel particulate filter are mainly comprised of metallic compounds generated during combustion and from corrosion in the exhaust system.

When the DPF becomes blocked a high pressure DTC sets in the PCM, the MIL (malfunction indicator lamp) is illuminated and limp home mode activated.

A blocked DPF can be a result of:

Excessive soot particles production

Multiple failed regeneration events

Mechanical or electrical failure of a related system or sub-system (for example EGR valve stuck open, charge air system leak, fuel injectors)

DPF Manual Regeneration or Operator Commanded Regeneration (If Equipped)

If the vehicle is operated with significant stationary operation, low speed drive cycles less than 10 - 15 minutes or the vehicle does not fully warm up, passive and active regeneration may not sufficiently clean the diesel particulate filter system. Operator commanded regeneration allows you to manually start regeneration of the diesel particulate filter at idle to clean the filter.

The operator commanded regeneration feature can be used when a message appears in the information display and the vehicle is not able to drive in a manner that allows effective automatic active regeneration or if you choose to manually start the regeneration of the diesel particulate filter manually while the vehicle is idle.

Operator Commanded Regeneration Precautions and Safe Exhaust Position

Stay clear of the exhaust tailpipe during regeneration. Hot exhaust gases can burn you badly.

Make sure that the louvers located at the tip of the exhaust are clear of any obstructions as they are used to introduce fresh air into the tailpipe to cool the exhaust gases as they leave the exhaust system.

Before starting operator commanded regeneration, do the following:

Shift into park (P) and apply the parking brake, on stable, level ground.
Park the vehicle outside of any structure.
Park the vehicle away from any obstructions and away from materials that can easily combust or melt, for example paper, leaves, petroleum products, fuels, plastics and other dry organic material.
Make sure there is a minimum of 1/8 tank of fuel.
Make sure all fluids are at proper levels.

To Start Operator Commanded Regeneration

WARNING: Stay clear of the exhaust tailpipe during regeneration. Hot exhaust gases can burn you badly.

NOTE: The operator commanded regeneration may be not able to use if the service engine soon warning lamp appears in the information display.

The operator commanded regeneration cannot be used until the diesel particulate filter load percentage has reached 100%. The diesel particulate filter load percentage fluctuates up and down when driving your vehicle due to active and passive regenerations.

Once operator commanded regeneration starts, engine speed increases to approximately 2000 rpm and the cooling fan speed increases. You will hear a change in audible sound due to engine speed and cooling fan speed increases.

It is not necessary to open the hood on the engine compartment. Once operator commanded regeneration completes, the engine speed returns to normal idling. The exhaust system remains very hot for several minutes even after regeneration is complete. Do not reposition the vehicle over materials that could burn until the exhaust system has had sufficient time to cool. Depending on the amount of soot collected by the diesel particulate filter, ambient temperature and altitude, operator commanded regeneration lasts approximately 30 minutes.

During the use of operator commanded regeneration, you may observe a light amount of white smoke. This is normal.

Operator Commanded Regeneration with Automatic Regeneration Control (If Equipped)

If the vehicle is operated with significant stationary operation, low speed drive cycles less than 15 minutes or the vehicle does not fully warm up, passive and active regeneration may not sufficiently clean the diesel particulate filter system. Automatic regeneration can be switched off until better driving conditions are available, for example steady high speed driving. It can then be switched back on to clean the diesel particulate filter.

SCR

SCR comprises of:

Urea Exhaust Injection Assembly
Exhaust Temperature Sensors
Engine Particulate Matter sensor and module
Engine NOx sensor and module
DEF Tank and Pump Assembly

The SCR (selective catalytic reduction system) improves the exhaust emissions and fuel efficiency by injecting Diesel Exhaust Fluid (DEF) into the exhaust system. DEF, is a 32.5% solution of urea in deionized water. At the inlet of the SCR, there is a port for the reductant injector which is followed by a multi-blade mixer. When DEF is introduced into the system, it atomizes and mixes evenly with exhaust gases in the multi-blade mixer. During this time, the heat of the exhaust gases causes the urea in the DEF to split into Carbon Dioxide (CO2) and ammonia. As the ammonia and NOx pass over the catalyst, a reaction takes place and the ammonia and NOx are converted to nitrogen and water. For additional information about the reductant system, Refer to: Engine Emission Control - Component Location .

Sound insulators and shields

Sound insulators and shields are attached to the underbody and exhaust system to protect the vehicle from exhaust system heat and should be inspected at regular intervals to make sure they are not dented or out of position. If a sound insulator and shield is damaged or shows evidence of deterioration, install a new sound insulator and shield. Some exhaust fasteners must be discarded and new ones installed as indicated in the procedures. Discard any damaged or heavily corroded fasteners and install new ones as necessary. Some exhaust fasteners are of a prevailing torque design. Use only new fasteners with the same part number as the original. Tighten the fasteners to the specified torque during reassembly to make sure of correct retention of exhaust components.

There are four (4) heat shields installed on the exhaust components, that heat shields are not released for service.