Exhaust System - Overview: Overview

WARNING: This page is about a different variant/trim than selected.

WARNING: Manual regeneration of the diesel particulate filter causes the exhaust gas to get very hot 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 an Oxidation Catalytic Converter (OC) 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 isolators. 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 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 exhaust system consists of:

a one-piece catalytic converter/DPF that is mounted to the TC.

a one-piece catalytic converter/DPF connected to the catalytic converter/ DPF and the selective catalyst reduction (SCR)/muffler with isolators.

a SCR/muffler with isolators connected to the and the tailpipe.

a tailpipe with a isolator connected to the muffler.

a fuel vaporizer system glow plug mounted in the catalytic converter/DPF.

a fuel vaporizer system fuel pump mounted on the front subframe.

The catalytic converter accelerates the heat-producing chemical reaction of components in the exhaust gases in order to reduce air pollutants. The catalytic converter is designed to provide a long life. No maintenance is necessary.

The DPF contains the Oxidation Catalytic Converter (OC). The DPF and the Oxidation Catalytic Converter (OC) are all in one assembly.

The OC which oxidizes hydrocarbons in the exhaust and generates heat for DPF regeneration. The DPF is a highly engineered aluminum titanate wall-flow catalyst that traps particulates. As soot gathers in the system it begins to restrict the filter and the filter needs to be periodically cleaned. The soot is cleaned by either passive or active regeneration. Both methods occur automatically and require no action from the driver/operator.

Passive regeneration occurs naturally as a result of normal engine operating conditions. During passive regeneration, the exhaust constituents/temperature are at an appropriate level where some soot is reduced or oxidized (burned) thus cleaning the filter.

Active regeneration, which is initiated by the PCM, occurs when there is not enough passive regeneration occurring due to vehicle drive patterns. In an active regeneration, the DPF is cleaned by raising the exhaust temperature to a point where the soot is burned away. After the soot is burned off, the exhaust temperature and back pressure (restriction) returns to normal levels.

The SCR improves the exhaust emissions and fuel efficiency by injecting a diesel exhaust fluid into the exhaust system. Diesel exhaust fluid, is a 32.5% solution of urea in deionized water. At the inlet of the SCR, there is a port for the diesel exhaust fluid injector which is followed by a grate diffuser and a twist mixer. When diesel exhaust fluid is introduced into the system, it atomizes in the grate diffuser and mixes evenly with exhaust gases in the twist mixer. During this time, the heat of the exhaust gases causes the urea in the diesel exhaust fluid to split into Carbon Dioxide (CO2) and ammonia. As the ammonia and NOx pass over the catalyst, a reduction 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 - System Operation and Component Description .

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. The sound insulators and shields for the muffler, muffler pipe, resonator and catalytic converter pipe are installed separately.

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.