Illustration 13

(1) Coolant temperature

(2) Exhaust back pressure

(3) NRS

(4) Injection control

(5) Injectors 1 and 2

(6) Water in fuel

(9) Inlet heater terminal

(10) Injectors 3 and 4

(11) Injectors 5 and 6

(12) Plug for inlet heater

(13) Relay

(14) Crankshaft position

(15) Injector drive connections

(16) ECM

(17) NRS drive

(18) Customer connection

(19) Low-pressure fuel

(20) Engine oil pressure

(21) Injection pressure regulator

(22) Oil temperature

(7) Inlet manifold air pressure

(8) Inlet air temperature

(23) Camshaft position connection

ECM

Reference Voltage (VREF)

The Electronic Control Module (ECM) monitors and

controls engine performance to ensure maximum

performance and adherence to emissions standards.

The ECM supplies a 5 V VREF signal to input sensors

in the electronic control system. By comparing the 5

V VREF signal sent to the sensors with the respective

returned signals, the ECM determines pressures,

positions, and other variables important to engine

and vehicle functions.

The ECM performs the following functions:

•  Provide Reference Voltage (VREF)

•  Condition input signals

The ECM supplies two independent circuits for VREF:

•  VREF (A) supplies 5 V to the engine sensors

•  VREF (B) supplies 5 V to the OEM wiring harness

•  Process and stores control strategies

•  Control actuators

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Signal Conditioner

Random Access Memory (RAM)

The signal conditioner in the internal microprocessor

converts analog signals to digital signals, squares up

sine wave signals, or amplifies low intensity signals

to a level that the ECM microprocessor can process.

RAM stores temporary information for current engine

conditions. Temporary information in RAM is  lost

when the ignition switch is turned to OFF or  when

ECM power is interrupted. RAM information includes

the following:

Microprocessor

•  Engine temperature

•  Engine rpm

The ECM  microprocessor stores operating

instructions (control strategies) and value  tables

(calibration parameters). The ECM compares stored

instructions and values with conditioned input values

to determine the correct  strategy for all engine

operations.

•  Accelerator pedal position

Actuator Control

Continuous calculations in  the ECM occur at

two different levels or  speeds: Foreground and

Background.

The ECM controls the  actuators by applying a

low-level signal (low side driver) or a high-level signal

(high side driver). When switched on, both drivers

complete a ground or power circuit to an actuator.

•  Foreground calculations  are faster than

background calculations and are normally more

critical for engine operation. Engine speed control

is an example.

Actuators are controlled in one of the following ways,

depending upon type of actuator:

•  Duty cycle (percent time on/off)

•  Switched on or off

•  Background calculations are normally variables

that change at slower rates. Engine temperature

is an example.

•  CAN messages

Diagnostic Trouble Codes (DTCs) are set  by the

microprocessor, if inputs or conditions do not comply

with expected values.

Actuators

The ECM controls engine operation with the following:

•  Valve for the NOx Reduction System (NRS)

•  Intake Air Heater (IAH) relay

•  Injection timing

Diagnostic strategies are also programmed into the

ECM. Some strategies monitor inputs continuously

and command the necessary outputs  for correct

performance of the engine.

Microprocessor Memory

The ECM microprocessor includes  Read Only

Memory (ROM) and Random Access Memory (RAM).

•  Injection pressure regulation valve

Valve for the NOx  Reduction System

(NRS) (if equipped)

Read Only Memory (ROM)

ROM stores permanent information for calibration

tables and operating strategies. Permanently stored

information cannot be changed or lost  by turning

the ignition switch OFF  or when ECM power is

interrupted. ROM includes the following:

The valve for the NOx Reduction  System (NRS)

controls the flow of  exhaust gases to the intake

manifold.

The valve for the NOx Reduction  System (NRS)

receives the desired valve position from the ECM

for the reduction of NOx.  The valve for the NOx

Reduction System (NRS) provides feedback to the

ECM on the valve position.

•  Application configuration, modes of operation, and

options

•  Engine Family Rating Code (EFRC)

•  Engine warning and protection modes

The valve for the NOx Reduction  System (NRS)

constantly monitors the valve position.  When an

NOx control error is detected, the valve for the NOx

Reduction System (NRS) sends a message to the

ECM and a DTC is set.

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Systems Operation  Section

Intake Air Heater (IAH) Relay

The Intake Air Heater  (IAH) system warms the

incoming air supply prior to  cranking to aid cold

engine starting.

The ECM is programmed  to energize the IAH

elements through the IAH relay while  monitoring

certain programmed conditions for engine coolant

temperature, engine oil temperature, and atmospheric

pressure.

The ECM activates  the IAH relay. The  relay

delivers VBAT to the  heater elements for a set

time, depending on engine coolant temperature and

altitude. The ground circuit is supplied directly from

the battery ground at all times.

Engine Sensors

Thermistor Sensors

A thermistor sensor varies electrical resistance with

changes in temperature. Resistance in the thermistor

decreases as temperature increases, and increases

as temperature decreases. Thermistors  have a

resistor that limits current in the ECM to a voltage

signal matched with a temperature value.

The top half of the  voltage divider is the current

limiting resistor inside the ECM. A thermistor sensor

has two electrical connectors, signal  return and

ground. The output of  a thermistor sensor is a

nonlinear analog signal.

Thermistor type sensors include the following:

•  Engine Coolant Temperature (ECT) sensor

•  Engine Oil Temperature (EOT) sensor

•  Inlet Air Temperature (IAT) sensor

•  Manifold Air Temperature (MAT) sensor

g02730803

Illustration 14

A typical example of a  schematic for the temperature sensors

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Systems Operation  Section

Engine Coolant Temperature (ECT) Sensor

•  Manifold Air Pressure (MAP) sensor

The ECM monitors the ECT  signal and uses this

information for the instrument panel temperature

gauge, coolant compensation, Engine  Warning

Protection System (EWPS), and IAH operation. The

ECT is a backup, if the EOT is out-of-range. The ECT

sensor is installed in the water supply housing, to the

right of the flat idler pulley assembly.

Engine Oil Temperature (EOT) Sensor

The ECM monitors the EOT signal  and uses this

information to control fuel quantity and timing when

operating the engine. The EOT signal  allows the

ECM to compensate for differences in oil viscosity for

temperature changes. The EOT sensor is located

in the rear  of the front cover, to the  left of the

high-pressure pump assembly.

Inlet Air Temperature (IAT) Sensor

The ECM monitors the IAT signal to control injector

timing and fuel rate during cold starts. The ECM also

uses the IAT signal to control NOx position. The IAT

sensor is installed in the air filter housing.

Manifold Air Temperature (MAT) Sensor

The ECM monitors the MAT signal for operation of

the NOx Reduction System (NRS). The MAT sensor

is located in the intake manifold, to the right of the

MAP sensor.

Variable Capacitance Sensors

Variable capacitance sensors measure pressure. The

pressure measured is applied to a ceramic material.

The pressure forces the ceramic material closer to a

thin metal disk. This action changes the capacitance

of the sensor.

The sensor is connected to the ECM by the VREF,

signal, and signal ground wires.

The sensor receives the VREF and returns an analog

signal voltage to the ECM. The ECM compares the

voltage with pre-programmed values to determine

pressure.

The operational range of a variable  capacitance

sensor is linked to the thickness of the ceramic disk.

The thicker the ceramic disk the more pressure the

sensor can measure.

Variable capacitance sensors include the following:

•  Engine Fuel Pressure (EFP) sensor

•  Engine Oil Pressure (EOP) sensor

•  Exhaust Back Pressure (EBP) sensor

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Systems Operation  Section

g02730805

Illustration 15

A typical example of a schematic  for the engine pressure sensors

Engine Fuel Pressure (EFP) Sensor

Magnetic Pickup Sensors

The ECM uses the EFP sensor  signal to monitor

engine fuel pressure and give an indication when the

fuel filter needs to be changed. The EFP sensor is

installed in the fuel filter housing on the left side of

the crankcase.

A magnetic pickup sensor contains a permanent

magnet core that is surrounded by a  coil of wire.

The sensor generates a voltage signal through the

collapse of a magnetic  field that is created by a

moving metal trigger. The movement of the trigger

then creates an AC voltage in the sensor coil.

Engine Oil Pressure (EOP) Sensor

Magnetic pickup sensors used include the following:

•  Crankshaft Position (CKP) sensor

The ECM monitors the EOP signal, and uses  this

information for the instrument panel pressure gauge

and EWPS. The EOP sensor is installed in the left

side of the crankcase, below the left side of the fuel

filter housing.

•  Camshaft Position (CMP) sensor

Exhaust Back Pressure (EBP) Sensor

The ECM monitors the exhaust pressure so that the

ECM can control the turbocharger, NOx Reduction

System (NRS), and intake throttle  systems. The

sensor provides feedback to the ECM  for closed

loop control of the turbocharger. The EBP sensor is

installed in a bracket mounted on the water supply

housing (Freon® compressor bracket).

Manifold Air Pressure (MAP) Sensor

The ECM monitors the MAP signal  to determine

intake manifold pressure (boost). This information

is used to control the turbocharger boost. The MAP

sensor is installed in the intake manifold, left of the

MAT sensor.

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g02730800

Illustration 16

A typical example of a schematic  for speed/timing sensors

Crankshaft Position (CKP) Sensor

The CKP sensor provides the ECM  with a signal

that indicates crankshaft speed and position. As the

crankshaft turns, the CKP sensor detects a 60 tooth

timing disk on the crankshaft. Teeth 59 and 60 are

missing. By comparing the CKP signal with the CMP

signal, the ECM calculates engine rpm and timing

requirements. The CKP sensor is installed in the top

left side of the flywheel housing.

Camshaft Position (CMP) Sensor

The CMP sensor provides the ECM with a signal that

indicates camshaft position. As the cam rotates, the

sensor identifies the position of the cam by locating

a peg on the cam. The CMP sensor  is installed in

the front cover, above and to the right of the water

pump pulley.

Micro Strain Gauge (MSG) Sensors

A Micro Strain Gauge  (MSG) sensor measures

pressure. Pressure to be measured exerts force on

a pressure vessel that stretches and compresses

to change resistance of strain gauges  bonded to

the surface of the pressure vessel. Internal sensor

electronics convert the changes in resistance to a

ratiometric voltage output.

The sensor is connected to the ECM by the VREF,

signal, and signal ground wires.

The sensor is powered by VREF received from the

ECM and is grounded through the ECM to a common

sensor ground. The ECM compares the voltage with

pre-programmed values to determine pressure.

The micro strain gauge type sensor is the following:

•  Injection Control Pressure (ICP)

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Systems Operation  Section

g02730804

Illustration 17

A typical example of a schematic  for injection control pressure sensor

Injection Control Pressure (ICP)

The ECM monitors the ICP  signal to determine

injection control pressure for engine operation. The

ICP signal is used to control the IPR valve. The ICP

sensor provides feedback to the ECM for  Closed

Loop IPR control. The  ICP sensor is under the

valve cover, forward of the No. 6 fuel injector in the

high-pressure oil manifold.

Switches

Switch sensors indicate position, level, or  status.

They operate open or closed, regulating the flow of

current. A switch sensor can be a voltage input switch

or a grounding switch. A voltage input switch supplies

the ECM with a voltage when it is closed. A grounding

switch grounds the circuit when closed, causing a

zero voltage signal. Grounding switches are usually

installed in series with a current limiting resistor.

Switches include the following:

•  Engine Coolant Level (ECL) (if equipped)

•  Water In Fuel (WIF)

g02730839

Illustration 18

A typical example of a  schematic for the water in fuel switch

Engine Coolant Level (ECL) (if equipped)

ECL is part of the Engine Warning Protection System

(EWPS). The ECL , , , switch is used in plastic deaeration

tanks. When a magnetic switch is open, the tank is

full.

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