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| Illustration 1 | g06237614 |
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(1) Diesel Oxidation Catalyst (DOC)
(2) Selective Catalytic Reduction (SCR) catalyst (3) Diesel Particulate Filter (DPF) (4) ARD body (5) Connection for the coolant (6) ARD head (7) Pilot fuel line (8) Spark plug (9) Relay for the Heated Nozzle (10) Line for combustion air (11) Exhaust from turbocharger (12) ARD combustion air valve (13) Compressed air from turbocharger (14) Ignition coil (15) ARD fuel manifold (16) In-line fuel filter (17) Electric priming pump (18) Primary fuel filter (19) Fuel from tank | |
The Clean Emissions Module (CEM) contains the Aftertreatment Regeneration Device (ARD), Diesel Particulate Filter (DPF) and Selective Catalytic Reduction (SCR) system. The CEM contains various mechanical and electrical components that reduce various exhaust emissions emitted from the engine. All the systems for the CEM are controlled by the engine ECM.
The two major functions of the clean emissions module are:
- Carbon Monoxide and hydrocarbon emitted from the engine are oxidized through the Diesel Oxidation Catalyst (DOC) and the particulate matter (soot) is trapped in the Diesel Particulate Filter (DPF). The trapped particulate matter is cleaned from the DPF through a catalytic reaction and by heating the filter through a process called Regeneration.
- NOx emissions emitted from the engine are reduced through a process called Selective Catalytic Reduction (SCR).
Aftertreatment Regeneration Device (ARD)
The ARD is primarily used to regenerate, or clean, soot from the DPF. The ARD is also used to heat and maintain the SCR system. The ARD is made up of fuel, air, and electrical subsystems. Regeneration is a process which uses diesel fuel and boost air from the turbocharger to create a high temperature flame. The heat from that high temperature flame is introduced to the inlet of the DPF.
The soot load on most Tier IV Final products is burned passively. This is due to the addition of the SCR. The SCR cleans up NOx, which allows the engine to produce more NOx. The engine now produces less soot since the higher NOx output allows soot to burn off at lower temperatures. For this reason active regeneration may not be required to burn soot. Regenerations will still be desired to maintain the ARD head and SCR system.
To regenerate the DPF at the right time, the ECM must know what the soot level is and how much time has passed since the last regeneration occurred. This time remaining until a regeneration must be performed is displayed on the dash as "Time To Regen" and has soot and time as an input. The soot input is a function of:
- Delta pressure measurement across the DPF
- Calculated model based on developed engine out soot measurements
The information gathered from these two inputs is converted into a percentage of soot output. Soot level can be viewed through Cat® Electronic Technician (ET).
Note: If the "Time To Regen" is driven by the timer, it will count down in real time. If driven by soot, it may count down slightly faster than real time depending on soot rate. About 95 percent of applications will be driven by the timer and not soot. If driven by soot, once the "Time To Regen" reads 0 the soot percent is at least 100 percent. Whenever "Time To Regen" reads 0, a regeneration must be performed.
There are four methods for triggering a regeneration:
Soot - The DPF will collect soot produced by the engine. An automatic regeneration will become active to reduce soot level. Details on how soot level is used to trigger regenerations are explained in "Regeneration Action Strategies" section.
Start-Up Regeneration - A start-up regeneration is initiated by the ECM after a cold engine start. This regeneration is performed to heat the system to a required temperature for Diesel Exhaust Fluid (DEF) dosing to begin. DEF dosing requirements are explained in Systems Operation, "DEF Dosing Control System" section.
SCR Maintenance - A regeneration is performed to maintain the SCR system. This regen is triggered when there is ammonia slip or poor NOx conversion. Details are explained in Systems Operation, "DEF Dosing Control System" section
ARD Maintenance - A regeneration is performed to maintain the ARD system. Fresh fuel must be flowed through the ARD head to allow a heated nozzle cycle. The heated nozzle cycle is used to clean the ARD nozzle. Details on the heated nozzle cycle are explained in the "Aftertreatment Fuel System" section.
Regeneration Action Strategies
The soot level percentage and time until a regen is required are generated by the ECM and used in determining:
- When to activate the DPF lamp
- When to activate the action lamp
- When to activate the action alarm (if equipped)
- When to activate the forced engine low idle strategy
- When to activate the forced engine shutdown strategy
- Regeneration lockout
- When a manual regeneration is allowed
- When an automatic regeneration is allowed
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| Illustration 2 | g06257907 |
Action Lamp - The action lamp will be illuminated at 100 percent soot level or "Time To Regen" is 0. The DPF lamp will remain on with the action lamp. A 3719-16 or 3750-17 code will become active. At 116% soot level a 3719 -0 code will become active. When the "Time To Regen" has been 0 for 6.4 hours, an action alarm will be activated (if equipped) and the engine will be 100% derated. A 3750-18 code will become active.
Automatic Regeneration - The ECM initiates automatic regenerations when criteria for one of the four regen trigger types are met. Depending on engine operating conditions, the regeneration will start as a low speed or high-speed regeneration. If a low speed regeneration has started and operating conditions change, the regeneration will transition to a high-speed regeneration without interruption.
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| Illustration 3 | g03749894 |
Check Engine Lamp (CEL): - This amber warning lamp will illuminate for any level 2 or level 3 fault that affects the engine. This includes any DPF-related issue that impacts the engine.
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| Illustration 4 | g03749907 |
DPF Lamp - The DPF lamp will be illuminated when soot level reaches 90 percent or "Time To Regen" is less than 3.2 hours.
Forced low idle strategy - The forced low idle strategy will be activated after the soot level has been at 116 percent for 5 minutes. Now, the engine will automatically drop to the programmed low idle speed. The only method to unlock the low idle speed is to cycle the key switch or perform a manual regeneration.
Forced engine shutdown strategy - The forced engine shutdown strategy will be activated when the soot level reaches 140 percent soot level. The engine will initially idle for 30 seconds before completely shutting down. A 3715-31 code will become active. The DPF can no longer be regenerated and must be replaced.
Manual Regeneration - Manual regeneration initiated by the force switch is only allowed when "Time To Regen" on display is reading less than 8 hours. If a manual regeneration is attempted before "Time To Regen" is less than 8 hours, then "Regen Not Required" will be displayed.
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| Illustration 5 | g03749898 |
Red Stop Lamp : Solid Flash - For industrial applications only, the red stop lamp will be illuminated solid whenever a level 3 event is active.
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| Illustration 6 | g03749900 |
Regeneration Active Lamp - This lamp will illuminate anytime regeneration is active.
Regeneration lockout - All forms of regeneration will be locked out from the operator once the soot level percent has been at 116 percent for 10 minutes. A 3714-31 code will become active. The engine will shut down but be allowed to restart. Regeneration can only be performed by using the "Manual DPF Regeneration" service procedure within Cat ET.
Note: Other factors are used in determining if regeneration will actually occur. The soot level thresholds simply tell the ECM when the different soot-based regenerations are allowed. The strategies to determine when regeneration will occur are discussed in the "Regeneration Types and Operating Criteria" section.
Regeneration is accomplished by supplying a regulated supply of diesel fuel and boost air to create a flame that is ignited by a spark. Once the flame is lit, fuel and air are all that are needed to maintain the flame. The flame detection temperature sensor determines if the flame was successfully lit. Once the flame is lit, the DPF inlet temperature sensor continuously monitors the temperature at the inlet of the DPF. As the temperature changes, the signal from the DPF inlet temperature sensor is sent back to the ECM. The ECM then calculates how much more or less fuel and air are needed to maintain the desired DPF inlet temperature. The specific systems related to regeneration are discussed later.
Regeneration Types and Operating Criteria
Automatic regenerations are designed so that no input is needed from the operator. There are two types of automatic regeneration. These regenerations are referred to as low speed regeneration and high-speed regeneration. Low speed regeneration and high-speed regeneration must meet specific criteria before the regeneration will automatically activate. This criteria is outlined below. Certain aspects of automatic regeneration can be configured though Cat ET. These aspects are discussed later in this section.
Low Speed Regeneration
Low speed regeneration occurs when the engine is in a stationary or non-working condition. Low speed regenerations are allowed between 80 and 116 percent soot level or when "Time To Regen" is less than 6.4 hours. The regenerations can occur up to 116% soot level. If "Time To Regen" is 0 and only based on time, not soot, regenerations will continue to be allowed. Low speed regenerations allow for the most precise control of fuel and airflow. Low speed regenerations require the least amount of fuel to be used as well as having the lowest duration times. The parameters listed below must be met to activate the low speed regeneration.
- Active Diagnostic or Event Codes - no active diagnostic or event codes can be active for the ARD fuel system, ARD air system, or ARD ignition system
- Engine Coolant Temperature - the engine coolant temperature must be greater than
40° C (104° F) if the ambient air temperature is greater than0° C (32° F) . If the ambient air temperature is less than0° C (32° F) , coolant temperature must be60° C (140° F) - Engine Startup Delay - the engine must be running for at least 2 minutes after a startup before regeneration will be allowed
- DPF Inlet Temperature - the DPF inlet temperature must be greater than 50C (122F)
Engine Speed
Engine speed must be within the low idle speed setting and less than 1500 rpm. If engine speed exits this window for 1 second, the low speed regeneration will terminate but may be allowed to transition to high-speed regeneration. Low speed to high-speed transition is discussed later. If the ambient temperature is less than
Fuel Delivery
Delivered fuel volume must be within 10 and 100 cubic millimeters of fuel. If fuel delivery exits this window for 1 to 2 seconds, the low speed regeneration will terminate but may be allowed to transition to high-speed regeneration. Low speed to high-speed transition is discussed later.
Engine Speed Control During Low Speed Regeneration
If the programmed low idle engine speed is less than 1000 rpm, the engine ECM may automatically elevate engine speed. The speed will be elevated to between 1000 and 1600 rpm. This change is needed to provide adequate airflow for regeneration. The elevated engine speed may remain for 30 seconds after the regeneration active lamp has turned off. In order for the engine ECM to elevate engine idle speed, pin 46 on the J1/P1 connector must be grounded. This connection can be hard wired to ground, or run through a switch that will connect the pin to ground when pressed. If pin 46 on the J1/P1 engine ECM connector is not grounded, engine speed will not elevate and regeneration will not occur.
Note: If a switch is used, the switch must be on continuous. A momentary switch will not keep the pin grounded for the duration that is needed.
High-Speed Regeneration
High-speed regeneration typically occurs when the engine is in normal operating mode. High-speed regenerations are allowed between 80 and 100 percent soot load or when "Time To Regen" is less than 6.4 hours. If "Time To Regen" is 0 and only based on time, not soot, regenerations will continue to be allowed. High-speed regenerations typically consume more fuel and require more time to complete compared to low speed regenerations. The parameters listed below outline the operating criteria that are monitored to activate and sustain high-speed regeneration.
In order for high-speed regenerations to take place, pin 47 on the J1/P1 connector on the engine ECM must be grounded. This connection can be hard wired to ground or grounded through a switch. A switch is provided on the Cat instrument panels. Refer to the Operation and Maintenance Manual, "Diesel Particulate Filter Regeneration" for more information.
The following parameters must be met for regeneration to occur:
- Active Diagnostic or Event Codes - no active diagnostic or event codes can be active for the ARD fuel system, ARD air system, or ARD ignition system
- Engine Coolant Temperature - the engine coolant temperature must be greater than
40° C (104° F) if the ambient air temperature is greater than0° C (32° F) . If the ambient air temperature is less than0° C (32° F) , coolant temperature must be60° C (140° F) - Engine Startup Delay - the engine must be running for at least 2 minutes after a startup before regeneration will be allowed
- DPF Inlet Temperature - the DPF inlet temperature must be greater than 50C (122F)
Engine speed (80-100% soot level)
Regeneration is allowed when engine speed is between 975 and 2350 rpm. Engine speed should not change more than 650 rpm per second. If speed changes by more than 650 rpm the regeneration will terminate.
Fuel Delivery (80-100% soot level)
Regeneration is allowed when delivered fuel volume is between 0 cubic millimeters and an upper limit defined by the engine power rating. The upper fuel limit is the torque fuel limit volume at each rpm.
Combustion Air Inlet Pressure (80-100% soot level)
The combustion air inlet pressure should not change more than
Engine Speed Control during High-Speed Regeneration
Most aspects of high-speed regeneration are transparent. If the engine is in normal working mode and the throttle is released, the low idle will be limited to 1000 rpm. Limiting the engine speed to 1000 rpm will maintain the regeneration. If the engine speed must be brought to the programmed low idle speed, pressing the disable regen switch will stop the regeneration. The engine will return engine speed to the programmed low idle speed.
Low Speed to High-Speed Regeneration Transition
If a low speed regeneration begins and the machine goes back to work, the regeneration will transition to a high-speed regeneration without interruption assuming all the parameters for allowing high-speed regenerations are met. Transition will be transparent to the operator.
Manual regeneration is accomplished by pressing the force regeneration switch. Manual regenerations can be performed when "Time To Regen" is less than 8 hours or soot level is between 80 and 116 percent. Manual regenerations are performed by pressing the force regeneration switch for 2 seconds. Refer to the Operation and Maintenance Manual, "Diesel Particulate Filter Regeneration" for more information. Manual regenerations can be done in the low speed regeneration region outlined above. All criteria described above is applicable to a manual regeneration in the low speed regeneration region.
Manual regenerations can be performed in the high-speed regeneration region on industrial applications ONLY. Manual regenerations are NOT allowed in the high-speed region on machine applications.
Aftertreatment Configuration Parameters
The aftertreatment system can be configured differently to suit the operation that the system is being used in. Configurations are also needed to assure the correct CEM is connected to the correct engine. The available configurations and the functions are the following:
ARD manual disable status
This status will disable all regenerations from occurring. Automatic and Manual regenerations will not work with this parameter set to "DISABLED". This parameter should be set to "NOT DISABLED" under normal conditions. This parameter is beneficial when servicing the system and regenerations are not desired.
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| Illustration 7 | g02435978 |
ARD auto regeneration enable status
This configuration has three settings. The settings are ENABLED, DISABLED, AND AUTOMATIC LOW SPEED REGENERATION ONLY. When configuration is set to ENABLED, all types of regeneration are available. When the configuration is set to DISABLED, only Manual regenerations will be available. When configuration is set to AUTOMATIC LOW SPEED REGENERATION ONLY, high-speed regeneration is not available. Low speed regeneration and manual regenerations are still available.
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| Illustration 8 | g02435980 |
Factory Installed Aftertreatment #1 Identification Number
This configuration contains the serial number of the CEM that is attached to the engine. This configuration is automatically programmed during initial assembly of the CEM to the engine. If this parameter needs reentered, the serial number can be found on the identification plate attached to the CEM.
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| Illustration 9 | g02435996 |
High Soot Load Aftertreatment protection enable status
This configuration is ENABLED by default. This configuration will activate the forced low idle speed strategy and forced engine shutdown strategy for high soot loading events. If this feature is "DISABLED", the forced low idle strategy and the forced engine shutdown strategy will not activate. These strategies must activate in the event of high soot loading.
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| Illustration 10 | g02436016 |
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| Illustration 11 | g06257925 |
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(1) ARD head
(2) Pilot fuel connection (3) Pilot fuel line (4) Pilot fuel pressure sensor (5) Pilot fuel solenoid valve (6) ARD fuel manifold (7) ARD manifold fuel filter fitting (8) Electric priming pump (9) Primary fuel filter (10) Fuel tank | |
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| Illustration 12 | g06257927 |
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(11) Diverter valve
(12) Fuel pressure regulator | |
Electric priming pump (8) is energized when regeneration is desired. Electric priming pump receives power from the battery. A relay is used to control power to the electric priming pump. The ECM sends a signal to the relay when regeneration is desired. When the relay is energized, battery power is sent to the electric priming pump. Electric priming pump pulls fuel from fuel tank (10) through the 10 micron primary fuel filter. Once fuel has exited the pump, the pressure regulator (12) regulates the pressure to
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| Illustration 13 | g06257929 |
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Front view (11) Diverter valve (13) Fuel flow to engine (diverter valve energized) | |
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| Illustration 14 | g06257934 |
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Side view (11) Diverter valve (14) Fuel flow to CEM (diverter valve de-energized) | |
Once fuel flow exits the pump housing, the fuel enters the ARD fuel manifold (6). As fuel enters the ARD fuel manifold, fuel is filtered by a stainless steel sintered filter. This filter can filter down to 40 micron. This filter is designed to collect any debris that may have entered the system during servicing.
As fuel flow continues through the ARD fuel manifold, the fuel takes a parallel flow path. One path goes to the pilot fuel solenoid valve (5). The pilot and main fuel solenoid valves are pulse width modulated solenoid valves controlled by the ECM. The pilot fuel solenoid valve is considered the primary fuel valve. Once the pilot fuel solenoid valve is fully open and more fuel is still desired, the main fuel solenoid valve will open. Once the fuel has passed through the pilot and main fuel solenoid valves, the fuel pressures are measured by a sensor for each circuit. When the circuit is operating in closed loop mode, the ECM uses these pressure signals to determine the proper amount of fuel. The amount of fuel is delivered to achieve the desired DPF inlet temperature.
Once the fuel exits the fuel manifold, the fuel enters the ARD head (1). The ARD head contains a single connection for pilot fuel (3). These connection fittings contain 40 micron sintered filter media. These filter fittings provide for protection against debris that may be introduced during servicing. As the fuel continues into the ARD head, the fuel opens two drain check valves. There is a drain check in the pilot fuel passage and the main fuel passage. These drain checks keep fuel trapped between the ARD fuel nozzle and pilot/main fuel valves when the system is not being used.
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| Illustration 15 | g06257977 |
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(15) Pilot drain check valve
(16) Fuel nozzle (17) Heating element | |
Next, the fuel enters the fuel nozzle. The fuel nozzle contains two separate passages for pilot fuel and main fuel. The fuel nozzle also contains a heating element. The heating element is used to clean accumulated carbon deposits from the end of the fuel nozzle. The heating element is powered through a solid-state relay mounted on the CEM electronics panel. The aftertreatment ECM periodically sends a signal to the relay causing battery voltage to travel to the heating element and energizing the coil. The coil can reach temperatures as high as
In order for the heater cycle to run the following parameters must meet minimum requirements: battery voltage, engine coolant temperature, and engine speed. The heated nozzle cycle runs for 60 minutes once the cycle has started. Many factors determine when to trigger a heater cycle. The two main factors are time between heater cycles and DPF regeneration completions. There are two time triggers for desiring a heated nozzle cycle. A heater cycle is first desired when time between heater cycles has reached 10 hours. The heater cycle will be desired after 10 hours but will only start after a successful complete regeneration has occurred. The second time trigger is when there has been 24 hours between heater cycles. After 24 hours the only requirement to allow cycle to run is that a minimum amount of main fuel has flown during regeneration in the last 30 minutes.
Besides the time triggers, a heated nozzle cycle may also be desired if regeneration fails to ignite so many times or loses combustion so many times. These thresholds are set up to trigger the heated nozzle cycle before a failed ignition or loss of combustion event code trips. In these cases a 30 minute heated nozzle cycle will trigger immediately after failure threshold is met.
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| Illustration 16 | g06257978 |
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(1) ARD body
(2) ARD head (3) Line for the combustion air (4) Exhaust from turbocharger (5) Exhaust manifold (6) Turbocharger (7) Compressed air to aftercooler (8) ARD combustion air valve (9) Combustion air inlet pressure sensor (10) Exhaust air to DOC and DPF | |
Exhaust Air
Exhaust air flows from the turbine housing to the ARD body. The exhaust air then flows through the Diesel Oxidation Catalyst (DOC) and the DPF. The exhaust air then exits through the SCR.
Combustion Air
The air used to supply the ARD head is taken from the turbocharger compressor outlet. The pressure of this air is measured at the inlet to the ARD combustion air valve by the combustion air inlet pressure sensor. The air is then metered by the ARD combustion air valve. The ARD combustion air valve contains a DC motor and analog position sensor. The aftertreatment ECM controls the ARD combustion air valve by sending it a desired opening position. The ARD combustion air valve moves the desired amount and the new valve position is transmitted back to the aftertreatment ECM.
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| Illustration 17 | g06257980 |
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(8) ARD combustion air valve
(11) Electronic Control Module (ECM) (12) Desired position command (13) Actual valve position data | |
Once the air has been metered by the ARD combustion air valve, the air enters the ARD head. The ARD head contains a swirling plate that is designed to agitate the air that is being mixed with the fuel. This agitated air allows for a precise burn of the air/fuel mixture.
Two lines circulate coolant in the ARD head. The coolant is used to extend the life of the O-ring for the ARD nozzle.
Diesel Particulate Filter (DPF) System
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| Illustration 18 | g06257983 |
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(1) DPF inlet and delta pressure sensors
(2) DPF inlet temperature sensor | |
The DPF system contains two types of filter media. The first filter media that exhaust gas is exposed to is the Diesel Oxidation Catalyst (DOC). This filter is a flow through style filter. The DOC is contained in the inlet section of the DPF cannister. The DOC filter contains platinum and palladium. The minerals aid in oxidizing hydrocarbons, carbon monoxide, and soluble organic fractions as the exhaust gas flows through the filter. The inlet section of the DPF cannister contains a temperature sensor, a pressure tap for the DPF inlet pressure sensor, and a DPF delta pressure sensor. All three of these components are before the DOC. The purposes of these components are:
DPF inlet temperature sensor
The DPF inlet temperature sensor measures the temperature entering the DPF cannister assembly. This temperature is used to control the ARD fuel and ARD air flow to maintain a desired DPF inlet temperature during regeneration.
DPF Delta Pressure sensor
The delta pressure sensor is also used to measure soot collected in the DPF. The delta pressure sensor is measuring the pressure drop across the DPF. Since the delta pressure sensor is measuring flow resistance across the DPF, the sensor will also detect ash loading.
DPF Inlet Pressure sensor
Used to measure the backpressure being generated by the DPF.
Once the exhaust gas flows through the DOC, the exhaust gas enters the DPF. The DPF is a catalyzed ceramic filter. The DPF uses a wall flow design. This design is a porous wall structure which allows clean exhaust gas to flow through, but does not allow soot or particulate matter to pass.
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| Illustration 19 | g02444298 |
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Cross section of DPF internals | |
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| Illustration 20 | g06257984 |
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Components for the ignition system (1) Spark plug (2) Ignition coil (3) Ignition wire | |
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| Illustration 21 | g06257989 |
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(4) ARD head
(5) Ignition wire (6) Ground point on the ARD combustion head | |
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| Illustration 22 | g06258308 |
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Typical ARD combustion head (7) Spark plug (8) Ground probe (9) Spark plug electrode | |
The ARD ignition system has two circuits. The primary circuit is between the ECM and the ignition coil. The secondary circuit is between the ignition coil and the ARD combustion head. The current flow through the primary circuit indicates the condition of the primary circuit and of the secondary circuit. The ECM monitors the current flow through the primary circuit. In this way, the ECM is able to detect problems with the primary circuit and the secondary circuit.
The ECM creates an ignition pulse 12 times each second whenever the engine speed is greater than 500 rpm. Wiring sends the signal to the primary side of the ignition coil. The ignition coil is on the panel for the electronics on the Clean Emissions Module (CEM).
The ignition coil converts the ignition pulse into a high-voltage signal. Ignition wire (5) connects the ignition coil output to the spark plug. The spark plug is threaded into the ARD combustion head. The spark jumps between the spark plug electrode (9) and ground probe (8) inside the ARD combustion head. The spark ignites the air/fuel mixture.
The ground wire ensures that the secondary ignition circuit is complete between the ARD combustion head and the ignition coil. The ground wire runs inside the insulation that is wrapped around ignition wire (5). The ground wire is connected to two ground points. One ground point (6) is on the ARD combustion head. One ground point is on the panel for the electronics near the ignition transformer.