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Engine Exhaust System Chevrolet Impala IX

Exhaust 2 illustrations ~3109 words

Fastener Tightening Specifications

ApplicationSpecification
MetricEnglish
Catalytic Converter Nut60 N.m44 lb ft
Exhaust Manifold Pipe to Catalytic Converter35 N.m26 lb ft
Exhaust Crossover Pipe Nut25 N.m18 lb ft
Exhaust Hanger Bracket Bolt25 N.m18 lb ft
Exhaust Manifold Bolt
First Pass15 N.m11 lb ft
Final Pass20 N.m15 lb ft
Exhaust Manifold Heat Shield Bolt (LS4)9 N.m80 lb in

Symptoms - Engine Exhaust

  1. Review the exhaust system description in order to familiarize yourself with the exhaust system components and the intended function of the components. Refer to «Exhaust System Description»(/chevrolet/impala/ix-2006-2016/remont/exhaust/#engine-exhaust-system__exhaust-system-description) .
  2. All diagnostics on a vehicle should follow a logical process. Strategy Based Diagnostics is a uniform approach for repairing all systems. The diagnostic flow is the place to start when repairs are necessary and may always be used in order to resolve a system problem. For a detailed explanation, refer to «Strategy Based Diagnosis»(/chevrolet/impala/ix-2006-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) .

Visual/Physical Inspection

  1. Inspect for aftermarket or non-OEM devices such as, but not limited to; tailpipe extensions, headers, and exhaust cutouts. Any aftermarket exhaust system devices could affect the operation and proper performance of the exhaust system.
  2. Verify the exact operating conditions under which the concern exists. Note factors such as engine RPM, engine temperature, engine load, and frequency of concern.
  3. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause any symptom.

Intermittent

Test the vehicle under the same conditions that the customer reported in order to verify the system is operating as designed.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

  1. Loss of power Refer to «Restricted Exhaust»(/chevrolet/impala/ix-2006-2016/remont/exhaust/#engine-exhaust-system)
  2. Poor acceleration Refer to «Restricted Exhaust»(/chevrolet/impala/ix-2006-2016/remont/exhaust/#engine-exhaust-system)
  3. Poor fuel economy Refer to «Restricted Exhaust»(/chevrolet/impala/ix-2006-2016/remont/exhaust/#engine-exhaust-system)
  4. Excessive smoke diesel Refer to «Restricted Exhaust»(/chevrolet/impala/ix-2006-2016/remont/exhaust/#engine-exhaust-system)
  5. Exhaust hissing noise Refer to «Exhaust Leakage»(/chevrolet/impala/ix-2006-2016/remont/exhaust/#engine-exhaust-system__exhaust-leakage)
  6. Exhaust popping noise Refer to «Exhaust Leakage»(/chevrolet/impala/ix-2006-2016/remont/exhaust/#engine-exhaust-system__exhaust-leakage)
  7. Exhaust rattle noise Refer to «Exhaust Noise»(/chevrolet/impala/ix-2006-2016/remont/exhaust/#engine-exhaust-system__exhaust-noise)
  8. Loud exhaust noise Refer to «Exhaust Noise»(/chevrolet/impala/ix-2006-2016/remont/exhaust/#engine-exhaust-system__exhaust-noise)
  9. Exhaust buzz, groan, hum noise Refer to «Exhaust Noise»(/chevrolet/impala/ix-2006-2016/remont/exhaust/#engine-exhaust-system__exhaust-noise)

Diagnostic Aids

For dual exhaust systems a quick check of exhaust flow will help determine which side of the exhaust system is restricted. The side that has less exhaust flow is the side that will be suspect, and the diagnosis should begin there.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. 4: The exhaust system has very low back pressure under normal conditions. If the exhaust system is restricted, a significant increase in the exhaust pressure is noticed on the J 35314-A exhaust back pressure gauge.Removing the heated oxygen sensor (HO2S) may set a DTC. When finishing this diagnostic table, be sure to clear all codes.
  2. 5: This step will isolate the catalytic converter from the remainder of the exhaust system.
  3. 8: Confirming that the condition has been fixed is essential. If the symptom still exists and the vehicle has a dual exhaust system, proceed to step 2 and repeat diagnostic procedure on the opposite exhaust pipe.
  4. 9: Confirming that the condition has been fixed is essential. If the symptom still exists, proceed to step 2 and repeat the diagnostic procedure.
StepActionValue(s)YesNo
1Did you verify the customers complaint?Go to Step 2
2Did you review the exhaust symptoms diagnostic information and perform the necessary inspections?Go to Step 3Go to Symptoms - Engine Exhaust
3Is the system equipped with dual exhaust?Go to Diagnostic AidsGo to Step 4
4WARNING: While engine is operating, the exhaust system will become extremely hot. To prevent burns avoid contacting a hot exhaust system. Remove the pre-catalyst heated oxygen sensor (HO2S). Refer to one of the following procedures: Heated Oxygen Sensor Replacement - Sensor 1 for the 3.5L engine Heated Oxygen Sensor Replacement - Sensor 1 for the 3.9L engine Install the J 35314-A exhaust back pressure gauge in place of the HO2S sensor. See Special Tools . Start and run the engine. Increase and monitor the engine speed at 2,500 RPM. Observe the exhaust system back pressure reading on the gauge. Does the reading exceed the specified value?9 kPa (1.25 psi)Go to Step 5Go to Step 9
5Turn the engine OFF and place the ignition in the lock position. Remove the J 35314-A . See Special Tools . Install the pre-catalyst HO2S. Refer to one of the following procedures: Heated Oxygen Sensor Replacement - Sensor 1 for the 3.5L engine Heated Oxygen Sensor Replacement - Sensor 1 for the 3.9L engine Remove the post-catalyst HO2S. Refer to one of the following procedures: Heated Oxygen Sensor Replacement - Sensor 2 for the 3.5L engine Heated Oxygen Sensor Replacement - Sensor 2 for the 3.9L engine Install the J 35314-A in place of the post HO2S. See Special Tools . Start and run the engine. Increase and monitor the engine speed at 2,500 RPM. Observe the exhaust system back pressure reading on the gauge. Does the reading exceed the specified value?9 kPa (1.25 psi)Go to Step 6Go to Step 7
6Inspect the exhaust system for the following conditions: Damage in the exhaust pipe Debris in the exhaust pipe Muffler or resonator internal failure Two-layer exhaust pipe separation Did you find and correct the condition?Go to Step 8
7Replace the catalytic converter. Refer to Catalytic Converter Replacement (LGD/LZE) . Did you find and correct the condition?Go to Step 8
8Remove the J 35314-A . See Special Tools . Install the post-catalyst HO2S. Refer to one of the following procedures: Heated Oxygen Sensor Replacement - Sensor 2 for the 3.5L engine Heated Oxygen Sensor Replacement - Sensor 2 for the 3.9L engine Clear any codes. Road test the vehicle in order to verify the repair. Did you correct the condition?System OKGo to Step 2
9Remove the J 35314-A . See Special Tools . Install the pre-catalyst HO2S. Refer to one of the following procedures: Heated Oxygen Sensor Replacement - Sensor 1 for the 3.5L engine Heated Oxygen Sensor Replacement - Sensor 1 for the 3.9L engine Clear any codes. Road test the vehicle in order to verify the repair. Did you correct the condition?System OKGo to Step 2
WARNING
While engine is operating, the exhaust system will become extremely hot. To prevent burns avoid contacting a hot exhaust system.

Exhaust Leakage

ProblemAction
WARNING: Refer to Hot Exhaust System Warning . NOTE: Refer to Symptoms - Engine Exhaust prior to beginning this table. DEFINITION: An exhaust leak may show stains at the area of the leak. The leak may be felt by holding a hand close to the suspected areas or using a smoke pencil. The leak may make a popping or hissing noise.
Misaligned or improperly installed exhaust system componentsCAUTION: Refer to Fastener Caution . Align and tighten the components to the specifications. Refer to Fastener Tightening Specifications .
Exhaust leaks at the following connections: Exhaust manifold to pipe Flanges Pipe clampsTighten the components to the specifications. Refer to Fastener Tightening Specifications .
Seals or gaskets leaking: Exhaust manifold to cylinder head Exhaust pipes to exhaust manifold Catalytic converter connection EGR connections AIR connections to the exhaust manifold or cylinder headReplace the leaking seal or gasket. Refer to the affected components procedure for service.
Exhaust manifold cracked or brokenReplace the exhaust manifold. Refer to Exhaust Manifold Replacement - Left Side (LGD/LZE) or Exhaust Manifold Replacement - Right Side (LGD/LZE) .
Exhaust system component connection welds leakingReplace the leaking component. Refer to the affected component procedure for service.
Muffler is damaged or leaking at the seamsReplace the affected muffler. Refer to Exhaust Muffler Replacement (Dual Outlet) or Exhaust Muffler Replacement (Single Outlet) .
WARNING
Refer to Hot Exhaust System Warning .
NOTE
Refer to Symptoms - Engine Exhaust prior to beginning this table.
CAUTION
Refer to Fastener Caution .

Exhaust Noise

ConditionAction
WARNING: Refer to Hot Exhaust System Warning . NOTE: Refer to Symptoms - Engine Exhaust prior to beginning this table. DEFINITION: An audible or physical noise due to a faulty component or damaged components causing a loose or misaligned exhaust system resulting in a rattle or vibration noise.
Popping or hissing noiseExhaust leak. Refer to Exhaust Leakage .
Loud exhaustCompare to a known good vehicle. Inspect for a damaged or failed muffler. Replace the faulty muffler. Refer to Exhaust Muffler Replacement (Dual Outlet) or Exhaust Muffler Replacement (Single Outlet) .
External rattle or vibration noiseInspect for a bent or loose hanger, loose heat shield, or loose clamp. Inspect for a exhaust pipe causing interference. Repair or replace the affected component. Refer to the affected component's service procedure.
Internal rattleTest the components by tapping with a rubber mallet to confirm a rattle. Replace the faulty catalytic converter, resonator, or muffler. Refer to one of the following procedures: Catalytic Converter Replacement (LGD/LZE) Exhaust Muffler Replacement (Dual Outlet) Exhaust Muffler Replacement (Single Outlet)
WARNING
Refer to Hot Exhaust System Warning .
NOTE
Refer to Symptoms - Engine Exhaust prior to beginning this table.

Removal Procedure

  1. Remove the engine mount strut bracket. Refer to «Engine Mount Strut Bracket Replacement - Left Side»(/chevrolet/impala/ix-2006-2016/remont/mechanical/#engine-mechanical-35l-repair-instructions-on-vehicle) .
  2. Remove the exhaust manifold heat shield bolts.
  3. Remove the exhaust manifold heat shield.
  4. Remove the exhaust crossover pipe heat shield bolts.
  5. Remove the exhaust crossover pipe heat shield.
  6. Remove the exhaust crossover pipe to left exhaust manifold nuts.
  7. Remove the exhaust manifold bolts.
  8. Remove the exhaust manifold.
  9. Remove and discard the exhaust manifold gasket.

Installation Procedure

  1. Install a NEW exhaust manifold gasket onto the cylinder head studs.
  2. Install the exhaust manifold.
  3. Install the exhaust manifold bolts. Tighten: Tighten the bolts to 20 N.m (15 lb ft).
  4. Install the exhaust crossover pipe to left exhaust manifold nuts. Tighten: Tighten the nuts to 20 N.m (15 lb ft).
  5. Install the exhaust crossover pipe heat shield.
  6. Install the exhaust crossover pipe heat shield bolts. Tighten: Tighten the bolts to 10 N.m (89 lb in).
  7. Install the exhaust manifold heat shield.
  8. Install the exhaust manifold heat shield bolts. Tighten: Tighten the bolts to 10 N.m (89 lb in).
  9. Install the engine mount strut bracket. Refer to «Engine Mount Strut Bracket Replacement - Left Side»(/chevrolet/impala/ix-2006-2016/remont/mechanical/#engine-mechanical-35l-repair-instructions-on-vehicle) .

Special Tools

J 39194-B Heated Oxygen Sensor Socket. See Special Tools .

  1. Remove the generator. Refer to «Generator Replacement (LGD/LZE)»(/chevrolet/impala/ix-2006-2016/remont/charging-system/#battery-charging-system-and-starting-system) .
  2. Remove the connector position assurance (CPA) retainer (3).
  3. Disconnect the heated oxygen sensor (HO2S) electrical connector (2).
  4. Remove the HO2S clip (1) from the ignition coil bracket.
  5. Remove the HO2S using the J 39194-B . See «Special Tools»(/chevrolet/impala/ix-2006-2016/remont/exhaust/#engine-exhaust-system) .
  6. Remove the exhaust manifold shield bolts.
  7. Remove the exhaust manifold shield.
  8. Remove the exhaust crossover pipe heat shield bolts.
  9. Remove the exhaust crossover pipe heat shield.
  10. Remove the exhaust crossover pipe to right exhaust manifold nuts.
  11. Remove the upper exhaust manifold bolts.
  12. Remove the catalytic converter. Refer to «Catalytic Converter Replacement (LGD/LZE)»(/chevrolet/impala/ix-2006-2016/remont/exhaust/#engine-exhaust-system) .
  13. Remove the lower exhaust manifold bolts.
  14. Remove the exhaust manifold.
  15. Remove and discard the exhaust manifold gasket.
  1. Install a NEW exhaust manifold gasket onto the cylinder head studs.
  2. Install the exhaust manifold.
  3. Install the lower exhaust manifold bolts. Tighten: Tighten the bolts to 20 N.m (15 lb ft).
  4. Install the catalytic converter. Refer to «Catalytic Converter Replacement (LGD/LZE)»(/chevrolet/impala/ix-2006-2016/remont/exhaust/#engine-exhaust-system) .
  5. Lower the vehicle.
  6. Install the upper exhaust manifold bolts. Tighten: Tighten the bolts to 20 N.m (15 lb ft).
  7. Install the exhaust crossover pipe to right exhaust manifold nuts.
  8. Install the exhaust crossover pipe heat shield.
  9. Install the exhaust crossover pipe heat shield bolts.
  10. Install the exhaust manifold shield.
  11. Install the exhaust manifold shield bolts. Tighten: Tighten the bolts to 10 N.m (89 lb in).
  12. Install the HO2S using J 39194-B . See «Special Tools»(/chevrolet/impala/ix-2006-2016/remont/exhaust/#engine-exhaust-system) . Tighten: Tighten the sensor to 42 N.m (31 lb ft).
  13. Connect the HO2S electrical connector (2).
  14. Install the CPA retainer (3).
  15. Install the HO2S clip (1) to the ignition coil bracket.
  16. Install the generator. Refer to «Generator Replacement (LGD/LZE)»(/chevrolet/impala/ix-2006-2016/remont/charging-system/#battery-charging-system-and-starting-system) .
  1. Remove the air cleaner outlet duct. Refer to «Air Cleaner Outlet Duct Replacement»(/chevrolet/impala/ix-2006-2016/remont/testing-diagnostics/#engine-controls-and-fuel-35l-repair-instructions) or «Air Cleaner Outlet Duct Replacement»(/chevrolet/impala/ix-2006-2016/remont/testing-diagnostics/#engine-controls-and-fuel-39l-repair-instructions) .
  2. Remove the exhaust crossover pipe heat shield bolts.
  3. Remove the exhaust crossover pipe heat shield.
  4. Remove the exhaust crossover pipe nuts.
  5. Remove the exhaust crossover pipe.
  6. Remove the exhaust crossover pipe seals.
  1. Install the exhaust crossover pipe seals to the exhaust manifolds.
  2. Install the exhaust crossover pipe.
  3. Install the exhaust crossover pipe nuts. Tighten: Tighten the nuts to 20 N.m (15 lb ft).
  4. Install the exhaust crossover pipe heat shield.
  5. Install the exhaust crossover pipe heat shield bolts. Tighten: Tighten the bolts to 10 N.m (89 lb in).
  6. Install the air cleaner intake duct. Refer to «Air Cleaner Outlet Duct Replacement»(/chevrolet/impala/ix-2006-2016/remont/testing-diagnostics/#engine-controls-and-fuel-35l-repair-instructions) or «Air Cleaner Outlet Duct Replacement»(/chevrolet/impala/ix-2006-2016/remont/testing-diagnostics/#engine-controls-and-fuel-39l-repair-instructions) .
  1. Remove the catalytic converter. Refer to «Catalytic Converter Replacement (LGD/LZE)»(/chevrolet/impala/ix-2006-2016/remont/exhaust/#engine-exhaust-system) .
  2. Remove and discard the exhaust manifold pipe gasket (2).
  3. Remove and discard the catalytic converter to muffler gasket (2).
  4. Remove and discard the catalytic converter to muffler seal.
  1. Install a NEW catalytic converter to muffler gasket (2).
  2. Install a NEW exhaust manifold pipe gasket (2).
  3. Install the catalytic converter. Refer to «Catalytic Converter Replacement (LGD/LZE)»(/chevrolet/impala/ix-2006-2016/remont/exhaust/#engine-exhaust-system) .

Note. The catalytic converter is serviced by replacing the entire assembly. Always replace the gaskets at the front and rear flanges when servicing the catalytic converter. Never install the original gasket.

  1. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#general-information__lifting-and-jacking-the-vehicle) .
  2. Remove the HO2S sensor 2. Refer to «Heated Oxygen Sensor Replacement - Sensor 2»(/chevrolet/impala/ix-2006-2016/remont/testing-diagnostics/#engine-controls-and-fuel-35l-repair-instructions) .
  3. Support the exhaust system.
  4. Remove the catalytic converter (3) to muffler nuts (1).
  5. Remove the catalytic converter hanger insulators.
  6. Remove the catalytic converter (2) to engine exhaust Manifold nuts (1).
  7. Reposition the muffler assembly rearward until the catalytic converter can be removed.
  8. Remove the catalytic converter (1) from the vehicle.
  9. Remove the catalytic converter gaskets.
  10. Clean and inspect the exhaust manifold and the exhaust pipe gasket mating surfaces.
  1. Install NEW gaskets to the catalytic converter and Muffler assembly.
  2. Reposition the muffler assembly rearward in order to position the catalytic converter (1) to the exhaust Manifold and muffler assembly.
  3. Install the catalytic converter (2) to the engine exhaust manifold nuts (1) and tighten to 35 N.m(26 ft lb).
  4. Install the catalytic converter (3) hanger insulators.
  5. Install the catalytic converter to muffler nuts (1) and tighten to 60 N.m(44 ft lb).
  6. Remove the support from the exhaust system.
  7. Install the HO2S sensor 2. Refer to «Heated Oxygen Sensor Replacement - Sensor 2»(/chevrolet/impala/ix-2006-2016/remont/testing-diagnostics/#engine-controls-and-fuel-35l-repair-instructions) .
  8. Lower the vehicle.
IMPORTANTThe muffler is serviced as a complete assembly and cannot be serviced separately.
  1. Remove the catalytic converter. Refer to «Catalytic Converter Replacement (LGD/LZE)»(/chevrolet/impala/ix-2006-2016/remont/exhaust/#engine-exhaust-system) .
  2. Support the exhaust system.
  3. With the aid of an assistant, remove the exhaust system from the exhaust hangers.
  4. Clean the catalytic converter and the muffler mating surfaces.
  1. With the aid of an assistant, install the muffler to the exhaust hangers.
  2. Remove the support from the exhaust system.
  3. Install the catalytic converter. Refer to «Catalytic Converter Replacement (LGD/LZE)»(/chevrolet/impala/ix-2006-2016/remont/exhaust/#engine-exhaust-system) .
IMPORTANTThe muffler is serviced as a complete assembly and cannot be serviced separately.
  1. Remove the catalytic converter. Refer to «Catalytic Converter Replacement (LGD/LZE)»(/chevrolet/impala/ix-2006-2016/remont/exhaust/#engine-exhaust-system) .
  2. Have an assistant support the muffler assembly.
  3. Remove the muffler assembly from the exhaust insulators.
  4. Clean the catalytic converter to muffler mating surfaces.
  1. Lubricate the insulators with spray lubricant.
  2. With the aid of an assistant, install the muffler assembly to the exhaust insulators.
  3. Install the catalytic converter. Refer to «Catalytic Converter Replacement (LGD/LZE)»(/chevrolet/impala/ix-2006-2016/remont/exhaust/#engine-exhaust-system) .
  1. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#general-information__lifting-and-jacking-the-vehicle) .
  2. Using a suitable jack, support the exhaust system, if necessary.
  3. Remove and discard the catalytic converter pipe hangers (1), if necessary.
  1. Install the NEW catalytic converter pipe hangers (1), if necessary.
  2. Remove the support from the exhaust system, if necessary.
  3. Lower the vehicle.
  1. Remove the catalytic converter. Refer to «Catalytic Converter Replacement (LGD/LZE)»(/chevrolet/impala/ix-2006-2016/remont/exhaust/#engine-exhaust-system) .
  2. Remove the heated oxygen sensor (HO2S) wiring harness from the clips on the catalytic converter heat shield.
  3. Drill out the catalytic converter heat shield rivets.
  4. Remove the catalytic converter heat shield.
  1. Position the catalytic converter heat shield to the underbody.
  2. Install NEW catalytic converter heat shield rivets.
  3. Install the HO2S wiring harness from the clips on the catalytic converter heat shield.
  4. Install the catalytic converter. Refer to «Catalytic Converter Replacement (LGD/LZE)»(/chevrolet/impala/ix-2006-2016/remont/exhaust/#engine-exhaust-system) .

Exhaust System Description

Note. Use of non-OEM parts may cause driveability concerns.

The exhaust system carries exhaust gases, treated by the catalytic converter, through a resonator, if applicable and into the exhaust muffler where exhaust noise is lessened.

In order to secure the exhaust pipe to the exhaust manifold, a flange and seal-joint coupling is utilized. The exhaust system may utilize a slip-joint coupling design with a clamp and a U-bolt or a flange connection with a gasket.

Exhaust hangers and rubber insulators help to support the weight of the exhaust pipe along with insulating any exhaust system vibration, rattle, or noise.

Exhaust hangers also space the exhaust system away from the underbody of the vehicle and allows the exhaust system to expand as the exhaust system warms up.

Exhaust heat shields are used to protect the body and other components from damage due to the heat from the exhaust system.

The exhaust system may be comprised of the following components

  1. Exhaust manifold
  2. Exhaust pipes
  3. Catalytic converters
  4. Exhaust muffler
  5. Exhaust resonator, if equipped
  6. Exhaust tail pipe, if equipped
  7. Exhaust hangers
  8. Exhaust heat shields

Resonator

Some exhaust systems are equipped with a resonator. The resonator, located either before or after the muffler, allows the use of mufflers with less back pressure. Resonators are used when vehicle characteristics require specific exhaust tuning.

Catalytic Converter

The catalytic converter is an emission control device added to the engine exhaust system in order to reduce hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx) pollutants from the exhaust gas.

The catalytic converter is comprised of a ceramic monolith substrate, supported in insulation and housed within a sheet metal shell. The substrate may be washcoated with 3 noble metals

  1. Platium (Pt)
  2. Palladium (Pd)
  3. Rhodium (Rh)

The catalyst in the converter is not serviceable.

Exhaust Particulate Filter

The exhaust particulate filter (EPF) captures diesel exhaust gas particulates, preventing their release into the atmosphere. This is accomplished by forcing particulate-laden exhaust (1) through a filter substrate of porous cells, which removes the particulates from the exhaust gas. The exhaust gas enters the filter, but because every other cell of the filter is capped at the opposite end, the exhaust particulates cannot exit the cell. Instead, the exhaust gas passes through the porous walls of the cell leaving the particulates trapped on the cell wall. The cleaned exhaust gas exits the filter through the adjacent cell. The EPF is capable of reducing more than 90 percent of particulate matter (PM).

Diesel Oxidation Catalyst

The diesel oxidation catalyst (DOC) (7) has two functions. One function is to reduce emissions of non methane hydro-carbons (NMHC) and carbon monoxide (CO), from the exhaust gases. The other function is to help start a regeneration event by converting the fuel-rich exhaust gases to heat. The engine control module (ECM) monitors the functionally of the DOC by determining if the exhaust gas temperature (EGT) sensor 1 (1) reaches a predetermined temperature during a regeneration event. The Diesel Particulate Filter (DPF) System Description DOC and the exhaust particulate filter (EPF) (6) are downstream of the turbocharger, and are two separate components under the vehicle.

Differential Pressure Sensor (DPS) and Pressure Lines

difference between the inlet and outlet of the exhaust particulate filter (EPF). When pressure difference has increased above a calibrated threshold, a high particulate loading condition is indicated. The ECM will command a regeneration event in order to restore the filter. If the pressure differential continues to increase across the exhaust filter without a regeneration event, the ECM will illuminate an EPF lamp or send a message to the driver information center (DIC) referring the customer to clean the exhaust filter. To clean the exhaust filter the vehicle must be driven under the conditions necessary for a regeneration to take place. If these lamps and messages are ignored, the ECM will eventually illuminate the malfunction indicator lamp (MIL) and revert to Reduced Engine Power which will require the vehicle to be serviced. The DPS sensor provides a voltage signal to the ECM on a signal circuit relative to the pressure differential changes in the EPF. The ECM converts the signal voltage input to a pressure value. The DPS pressure lines (2) are connected before and after the EPF. To provide the pressure sensor with accurate back pressure measurements, the DPS pressure lines should have a continuous downward gradient without any sharp bends.

Exhaust Gas Temperature Sensors

The ECM uses two exhaust gas temperature (EGT) sensors to measure the temperature of the exhaust gases at the inlet and outlet of the exhaust particulate filter (EPF). The EGT sensors are variable resistors, when the EGT sensors are cold, the sensor resistance is low, and as the temperature increases, the sensor resistance increases. When sensor resistance is high, the ECM detects a high voltage on the signal circuit. When sensor resistance is low, the ECM detects a lower voltage on the signal circuit. Proper EGTs at the inlet and outlet of the EPF are crucial for proper operation and for initiating the regeneration process. A temperature that is too high in the EPF will cause the EPF substrate to melt or crack. The ECM monitors the temperatures at the EPF inlet and outlet to regulate EPF temperatures.

Normal Regeneration

Regeneration is the process of removing the captured particulates through incineration within the exhaust particulate filer (EPF). Elevated temperatures are created in the diesel oxidation catalyst (DOC) through a calibrated strategy in the engine control system. Regeneration occurs when the ECM calculates that the particulate level in the filter has reached a calibrated threshold using a number of different factors, including engine run time, distance traveled, fuel used since the last regeneration, and the exhaust differential pressure. In general, the vehicle will need to be operating continuously at speeds above 48 km/h (30 mph) for approximately 20-30 minutes for a full and effective regeneration to complete. During regeneration the exhaust gases reach temperatures above 550°C (1,022°F). The ECM monitors the EGT sensors during regeneration. If the sensors indicate that regeneration temperatures are exceeding a calibrated threshold, regeneration will be temporally suspended until the sensors return to a normal temperature. If EGT temperatures fall below a normal calibrated threshold, regeneration will be terminated and a corresponding DTC should set. If a regeneration event is interrupted for any reason, it will continue, including the next key cycle, when the conditions are met for regeneration enablement. Normal regeneration is transparent to the customer.

Service Regeneration

WARNINGTailpipe outlet exhaust temperature will be greater than 300°C (572°F) during this procedure. To help prevent personal injury or property damage from fire or burns, perform the following: Do not connect any shop exhaust removal hoses to the vehicle tailpipe. Park the vehicle outdoors and keep people, other vehicles, and combustible material away during this procedure. Do not leave the vehicle unattended.

A scan tool is an essential tool that is required for service regeneration. Commanding a service regeneration is accomplished using the output control function. The vehicle will need to be parked outside the facility and away from nearby objects, such as other vehicles and buildings, due to the elevated exhaust gas temperature at the tail pipe during regeneration. The service regeneration can be terminated by applying the brake pedal, commanding service regeneration OFF using the scan tool, or disconnecting the scan tool from the vehicle.

Regeneration Process

A number of engine components are required to function together for the regeneration process to be performed. These components are the fuel injectors, turbocharger, IA valve, fuel pressure control, and the intake air heater (IAH). The regeneration process consists of several stages: Warming up the diesel oxidation catalyst (DOC) to 350°C (662°F) by performing the following

  1. Reducing air flow with the intake air valve
  2. Increasing or decreasing boost pressure with the turbocharger, depending on engine load
  3. Elevating the engine speed
  4. Reduce fuel rail pressure
  5. Retard fuel injection timing
  6. Add late fuel injection pulses. The added fuel is not combusted but is oxidized by the DOC and exhaust particulate filter (EPF) to create heat.

Ash Loading

Ash is a non-combustible by product from normal oil consumption. Low Ash content engine oil (CJ-4 API) is required for vehicles with the exhaust particulate filter (EPF) system. Ash accumulation in the EPF will eventually cause a restriction in particulate filter. Regeneration will not burn off the ash, only particulate matter is burned off. An ash loaded EPF will need to be removed from the vehicle and cleaned or replaced.

Muffler

The exhaust muffler reduces the noise levels of the engine exhaust by the use of tuning tubes. The tuning tubes create channels inside the exhaust muffler that lower the sound levels created by the combustion of the engine.

Illustration Tool Number/ Description J 35314-A Exhaust Back Pressure Gauge J 39194-B Heated Oxygen Sensor Wrench

Scheme 1

Scheme 1: Special Tools
Scheme 1: Special Tools

Scheme 2

Scheme 2
Scheme 2