Air Intake Heater (AIH)
Intake manifold air heater is used to warm intake air during cold starting conditions to eliminate the need for glow plugs. Intake manifold air consists of 2 grid heaters installed between air inlet housing and intake manifold cover.
Scheme 34
Powertrain Control Module (PCM) energizes intake manifold air heater relays to provide voltage to intake manifold air heater before and after starting depending on input signals from intake manifold air temperature sensor, engine speed sensor and vehicle speed. Intake manifold air heater relays are not energized when intake manifold air temperature is greater than 59°F (15°C) or during engine cranking. Intake manifold air heater relays are mounted on inner wheelwell, below driver's side battery.
Scheme 35
Intake manifold air temperature sensor monitors intake manifold air temperature and delivers an input signal to PCM for controlling intake manifold air heater. Intake manifold air temperature sensor is located in intake manifold cover.
Exhaust Gas Recirculation (EGR)
EGR system is used to reduce exhaust emissions. EGR system consists of EGR valve, EGR tube, EGR valve vacuum regulator solenoid and EGR valve one-way check valve. EGR valve and EGR tube allow exhaust gases to be recirculated into the air intake. EGR valve operation is controlled by EGR valve vacuum regulator solenoid. EGR valve regulator solenoid controls vacuum supply from vacuum pump to the EGR valve for EGR valve operation. The Powertrain Control Module (PCM) uses input signals from engine coolant temperature sensor, intake manifold air temperature sensor and Throttle Position (TP) sensor for controlling operation of EGR valve vacuum regulator solenoid. EGR valve one-way check valve is used to quickly release vacuum to EGR valve if EGR system operation is shut off. EGR system operates if vacuum pump is operating, PCM determines engine coolant temperature is more than 140°F (60°C), but less than 220°F (104°C), and intake air temperature is more than 20°F (6.6°C), but less than 170°F (76.7°C). EGR system will shut off if PCM determines a rapid acceleration is occurring, throttle is at wide open position, or throttle remains at the same position for 2 continuous minutes to indicate idle or normal cruising speed. If certain problems exist in the EGR system, a Diagnostic Trouble Code (DTC) will be stored in the PCM for system diagnosis.
Scheme 36
The Pickup Aftertreatment consists of a Closed Coupled Catalyst (CCC) The CCC is a Diesel Oxidation Catalyst (DOC) that is mounted very close to the turbocharger exhaust outlet. It is a metallic flow through substrate coated with a catalyst washcoat that is essential to the integrated operation of the aftertreatment assembly. The close coupled DOC treats engine exhaust gases by converting harmful carbon monoxide, unburned hydrocarbons and other compounds into water, carbon dioxide and heat. The ability to create heat is an important part of the system regeneration process.
NOx ADSORBER CATALYST (NAC): The NAC is located downstream of the CCC. Using the heat and exhaust constituents coming from the CCC, the NAC traps various oxides of nitrogen, and then converts those into Carbon Dioxide, Nitrogen (N2) and water via a regeneration process controlled by the engine's electronic control module (ECM). The NAC also plays a role in reducing non-methane hydrocarbons (NMHC) from the exhaust gas.
DIESEL PARTICULATE FILTER (DPF): The diesel particulate filter (DPF) is a wall-pass ceramic filter substrate coated with a catalyst washcoat. It is located just downstream of the NAC. Exhaust gases flow from the NAC into the catalyzed diesel particulate filter (DPF) which traps and accumulates particulate matter, and further treats the exhaust gases to reduce any remaining unburned hydrocarbons and other harmful compounds. The trapped particulate matter will be periodically removed from the DPF via a regeneration process controlled by the engine's electronic control module (ECM).
The Cab Chassis Aftertreatment consists of a combination diesel oxidation catalyst (DOC)/Diesel Particulate Filter (DPF). The diesel oxidation catalyst (DOC) is a ceramic flow through substrate coated with a catalyst washcoat that is integral to the DOC/Diesel Particulate Filter (DPF) assembly. The close coupled DOC treats engine exhaust gases by converting harmful carbon monoxide, unburned hydrocarbons and other compounds into water, carbon dioxide and heat.
Exhaust gases travel from the engine turbocharger through the front exhaust pipe into the Catalytic Converter which treats the exhaust gas by converting harmful carbon monoxide, unburned hydrocarbons and other compounds into water, carbon dioxide and heat.
The exhaust gases are then forced through the muffler for noise control. From the muffler the exhaust gases flow through the tail pipe and out into the ambient atmosphere.
The air heater element is used to heat incoming air to the intake manifold. This is done to help engine starting and improve driveability with cool or cold outside temperatures.
Electrical supply for the air heater element is controlled by the Engine Control Module (ECM) through the air heater relay. Refer to Intake Manifold Air Heater Relay for more information.
A heavy-duty cable connects the air heater element to the air heater relay. This cable will supply 12-volts to an individual heating element within the heater block assembly.
The following chart displays the pre-heat, or turn-on times (in seconds) of the wait-to-start lamp. If the intake manifold temperature is above 66.09 degrees Fahrenheit, the wait-to-start lamp will not illuminate. Consequently, the intake air heater element will not be activated.
| Manifold Temperature At: (In Degees° F) | Pre-Heat Time (Seconds) |
|---|---|
| 40.09 | 30.0 |
| 20.00 | 30.0 |
| 0.00 | 30.0 |
| 0.09 | 15.0 |
| 15.00 | 15.0 |
| 15.09 | 10.0 |
| 32.00 | 10.0 |
| 50.00 | 10.0 |
| 66.00 | 10.0 |
| 66.09 | 00.0 |
WAIT-TO-START LAMP TURN-ON TIMES
The Closed Crankcase Ventilation System (CCV) consists of several parts to make it functional. One part is the filter. The filter is serviceable and prevents oil mist from entering the discharge tube of the CCV system. It is not cleaned, but replaced at 60,000 mile intervals.
Scheme 37
The crankcase breather assembly is integrated into the cylinder head cover (3) and is serviced separately. The external fittings (2) to the breather tube and breather drain tube are serviceable.
The crankcase breather assembly is integrated into the cylinder head cover and corresponding breather cover. Crankcase gasses travel into the breather cavity under the breather cover where they pass through a filtering media (serviceable maintenance component) which separates the oil from the crankcase gasses. The oil drains back into the engine block through two hoses (2) on the left side of the engine.
The crankcase gasses are directed through the Crankcase Depression Regulator (CDR) valve which allows the system to maintain a constant positive pressure in the crankcase. The CDR valve is a non-serviceable component located on the underside of the breather cover. Clean crankcase gasses flow from the CDR valve into the fresh air side of the turbocharger compressor.
Scheme 38
The closed crankcase ventilation valve is used to vent the crankcase gases back into the intake of engine. If the crankcase ventilation filter becomes too restrictive, under high intake vacuum situations, the closed crankcase ventilation prevents the engine from siphoning crankcase gases/oil from the crankcase of the engine. The closed crankcase ventilation valve is located under the crankcase ventilation filter cover at the top of the engine.
The CCV system reroutes crankcase ventilation (blow-by) gases from the breather assembly back into the engine intake airflow to be used for combustion. The crankcase ventilation system uses a coalescing filter (2) which captures and filters crankcase blow-by gases and then returns oil directly to the sump.
The Closed Crankcase Ventilation System (CCV) consists of several parts to make it functional. One part is the breather element (1). The breather element (1) is serviceable and prevents oil mist from entering the discharge tube of the CCV system. The breather element (1) should be replaced at 60,000 mile intervals.
Scheme 39
Crankcase gasses travel into the breather cavity under the breather cover where they pass through a filtering media (serviceable maintenance component) which separates the oil from the crankcase gasses. The oil drains back into the engine block through two hoses (2) on the left side of the engine.
The crankcase gasses are directed through the Crankcase Depression Regulator (CDR) valve which allows the system to maintain a constant positive pressure in the crankcase. The CDR valve is a non-serviceable component located on the underside of the breather cover. Clean crankcase gasses flow from the CDR valve into the fresh air side of the turbocharger compressor.
The EGR (Exhaust Gas Recirculation) system is designed to reduce NOx in the exhaust system by reducing combustion temperatures. This is done by introducing inert gas (exhaust) into the combustion process. The intake air charge is diluted by a precisely metered amount of exhaust gas for the operating mode. For example at idle and part throttle, more EGR is introduced than at high-speed cruise conditions. A cooler (2) reduces the temperature of the exhaust gas before it is combined with the intake air, which increases the ability of the existing volume of inert gas to reduce NOx. The EGR cooler is cooled by the engine coolant.
Scheme 40
The EGR system contains the following components
- EGR Cooler (2)
- EGR Valve Assembly (5)
- EGR Valve Crossover Tube (4)
- EGR Temperature Sensor (7)
- EGR Valve Actuator (6)
- EGR Air Flow Control Valve (8)
EGR is active at low load and speed ranges. Control of EGR flow is based on engine load and engine speed. The ECM (Engine Control Module) gathers information from engine input sensors, and after evaluating the input signals, uses a stored performance map to operate the EGR Valve Actuator (2) and EGR Airflow Throttle Control Valve (3). The calculation allows for a precise EGR flow rate.
Scheme 41
The EGR Valve Assembly (1) is located at the left front of the engine, in the upper corner of the intake manifold. The EGR valve has two poppet valves connected by a valve shaft. Cooled exhaust gases flow from the EGR cooler to the center of the valve. When the valves open, exhaust gasses flow into the intake air stream from both the top and the bottom of the passage.
The EGR valve motor (actuator) (2) is a three-phase, brushless DC motor controlled by the ECM. The motor assembly also contains three Hall-effect sensors that detect EGR valve position.
Heated Oxygen Sensor (HO2S)
Two different six-wire O2 sensors are used. These sensors are titled 1/1 upstream (1), and 1/2 downstream (2).
O2 Sensor Locations. Scheme 42
A separate O2 Sensor Module (1) is also used.
O2 Sensor Module Location. Scheme 43
The engine aftertreatment system monitors the O2 content in the diesel engine exhaust. The ECM monitors the exhaust gases for oxygen content and varies the rich/lean fuel mixture of the intake air fuel mixture to adjust the system. This diagnostic monitors the status message broadcast by the O2 Sensor Module (1) for the upstream O2 sensor's internal heater circuit. The ECM will set the fault if it receives a FMI (Failure Mode Indicator) message from the O2 Sensor Module. The ECM will illuminate the MIL lamp immediately when the diagnostic runs and fails. The ECM will turn off the MIL lamp diagnostic runs and passes in four consecutive drive cycles.
The Pickup Aftertreatment consists of a Closed Coupled Catalyst (CCC) The CCC is a Diesel Oxidation Catalyst (DOC) that is mounted very close to the turbocharger exhaust outlet. It is a metallic flow through substrate coated with a catalyst washcoat that is essential to the integrated operation of the aftertreatment assembly. The close coupled DOC treats engine exhaust gases by converting harmful carbon monoxide, unburned hydrocarbons and other compounds into water, carbon dioxide and heat. The ability to create heat is an important part of the system regeneration process.
NOx ADSORBER CATALYST (NAC): The NAC is located downstream of the CCC. Using the heat and exhaust constituents coming from the CCC, the NAC traps various oxides of nitrogen, and then converts those into Carbon Dioxide, Nitrogen (N2) and water via a regeneration process controlled by the engine's electronic control module (ECM). The NAC also plays a role in reducing non-methane hydrocarbons (NMHC) from the exhaust gas.
DIESEL PARTICULATE FILTER (DPF): The diesel particulate filter (DPF) is a wall-pass ceramic filter substrate coated with a catalyst washcoat. It is located just downstream of the NAC. Exhaust gases flow from the NAC into the catalyzed diesel particulate filter (DPF) which traps and accumulates particulate matter, and further treats the exhaust gases to reduce any remaining unburned hydrocarbons and other harmful compounds. The trapped particulate matter will be periodically removed from the DPF via a regeneration process controlled by the engine's electronic control module (ECM).
The Cab Chassis Aftertreatment consists of a combination diesel oxidation catalyst (DOC)/Diesel Particulate Filter (DPF). The diesel oxidation catalyst (DOC) is a ceramic flow through substrate coated with a catalyst washcoat that is integral to the DOC/Diesel Particulate Filter (DPF) assembly. The close coupled DOC treats engine exhaust gases by converting harmful carbon monoxide, unburned hydrocarbons and other compounds into water, carbon dioxide and heat.
Exhaust gases travel from the engine turbocharger through the front exhaust pipe into the exhaust system Aftertreatment. The Aftertreatment consists of the Diesel Oxidation Catalyst (DOC) and a Diesel Particulate Filter. The DOC treats the exhaust gas by converting harmful carbon monoxide, unburned hydrocarbons and other compounds into water, carbon dioxide and heat.
The partially treated exhaust gases from the DOC flow into the catalyzed Diesel Particulate Filter (DPF) which traps and accumulates particulate matter (soot) and further treats the exhaust gases to reduce harmful compounds. The trapped particulate molecules will be periodically removed from the DPF through a thermal regeneration process initiated by the engine's electronic controls.
The exhaust gases are then forced through the muffler for noise control. From the muffler the treated exhaust gases flow through the tail pipe and out into the ambient atmosphere.
The task of the Exhaust Gas Recirculation (EGR) is to regulate the fresh air supply to the engine by means of the exhaust gas recirculation system, in favor of clean combustion. The EGR system reduces oxides of nitrogen (NOx) in the engine exhaust. This is accomplished by allowing a predetermined amount of hot exhaust gas to recirculate and dilute the incoming charge air.
A malfunctioning EGR system can cause engine stumble, sags, or hesitation, rough idle, engine stalling and poor driveability.
The system consists of
- A EGR valve assembly. The valve is located on the left side of the engine below the intake manifold.
- A EGR Cooler. The cooler is located on the left side of the engine below the intake manifold.
- A EGR air flow control valve. The EGR air flow control valve is located in the air inlet between the charge air inlet and the intake manifold. The air control valve is used to increase the EGR flow rate at low engine speeds.
- The ECM operates and monitors the EGR valve and air flow control valve. The ECM is located in the left-rear side of the engine compartment.
The ECM will monitor and determine the positioning of the EGR valve and air control valve by internal programming defined during engine development. This will depend on inputs from the engine coolant temperature, engine load, fuel quantity, throttle position and engine speed sensors. The air control valve blends the incoming charge air and the cooled and recirculated EGR gasses, to be used again in the combustion chamber.
Exhaust gas recirculation will begin in this order when
- The ECM determines that EGR system operation is necessary.
- The inlet seat (poppet valve) at the bottom of the EGR valve opens to dilute and recirculate exhaust gas back into the intake manifold.
- The EGR Cooler further cools the hot exhaust gasses before recirculation.
The EGR system will be shut down by the ECM after 60 seconds of continuous engine idling to improve idle quality and the air flow control valve will close completely when the vehicle is shut off to assist with engine shake on shut down.
Crankcase Ventilation Breather
The crankcase ventilation breather is a three staged, filtered, oil separating breather with a oil return passage into the cylinder head cover. The oil separator removes oil from the blow by gasses to reduce MAF sensor contamination.
The EGR system can provide up to 35% exhaust gas recirculation. The EGR operates during all engine speed and load conditions. At wide open throttle, it provides a 5% recirculation rate. The EGR shuts down during high engine idle to avoid carbon build up on the valve. The EGR also deactivates if the EGR temperature is too high. The EGR also has a self cleaning function that opens and closes twice after the engine has been shut off to eliminate soot deposits.
Apart from the charge air distribution manifold and the mixing chamber, the intake manifold also includes a finned EGR cooler. Coolant flows through the cooler to reduce the temperature of the recirculated gas after it was cooled by running through the cylinder head. The management of this temperature significantly reduces emissions.
Scheme 44
Exhaust gas recirculation reduces the quantity of fresh air supplied to the cylinders per stroke without having to throttle the air supply. Exhaust gas is recirculated during all engine speed and engine load conditions. As a result, emissions are reduced. If a quantity of exhaust gas is mixed with the air that is to be used to burn the fuel in the cylinders, the oxygen content is reduced because the exhaust gas is low in oxygen. The result is that the combustion rate is reduced, as is the combustion temperature. This reduces the quantity of NOx that are emitted in the exhaust gas.
The ECM power supply relay has a power off delay feature. The relay is powered off approximately 15 seconds after the ignition switch is turned off. This allows for the self-cleaning function of the EGR valve and a function check of the sensors for diagnosis purposes.
Scheme 45
The mass of the air supplied to the cylinders per stroke is the decisive factor for determining the optimum quantity of exhaust gas for the operating condition. This is calculated from the Mass Air Flow sensor information.
The ECM evaluates this signal as well as that from the Charge Air Pressure sensor, and outputs a PWM signal in accordance with one of the maps stored in it. The signal is sent to the exhaust gas recirculation valve. The map is formulated to keep the NOx as low as possible. The EGR valve is actuated by an electric positioning motor and has a self cleaning function. Every time the ignition switch is turned off, the valve rotates twice to eliminate any carbon deposits.
Valve Cooler
The exhaust gas recirculation (EGR) cooler is an integrated part of the EGR valve. Coolant flows around the exhaust gasses, cooling them before they are remixed with the incoming air and reburned in the combustion chamber.
The EGR valve and Cooler are serviced as an assembly.
Scheme 46
The Exhaust Gas Recirculation (EGR) Air Flow Valve Actuator and Resonator are located in the air intake tube between the turbocharger intercooler and the intake manifold. The EGR Air Flow Valve is controlled by the ECM. Refer to the appropriate engine diagnostic procedures for DTCs related to the EGR Airflow Valve Actuator.
The Exhaust Gas Recirculation (EGR) throttle valve adjusts the flow of fresh air into the engine during EGR operation. A signal from the Engine Control Module (ECM) controls the operation of the EGR throttle valve. The position at which the ECM will set the valve depends on the blended quantity of exhaust gas that needs to be recirculated into the engine in order for the exhaust gas to remain with the target emission level, which the ECM calculates based on input received from the oxygen sensors. When not actuated, the EGR throttle valve is in the open position.
Positive Crankcase Ventilation (PCV)
Located on the rear of the right cylinder head cover is a positive crankcase ventilation (PCV) valve (1). Internal engine vapor is captured, the solid particulates are separated by a diffuser located on the right exhaust camshaft, and the vapor is reused during the combustion process.
