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Part 5 of 6 in a series of articles outlining the Features, Descriptions, Unique Service Procedures, and General Diagnostics of the 6.0L DIT Power Stroke
From International Truck & Engine Corporation Publication
6.0 DIT Power Stroke
Generation II Electrical Components Overview
The PCM uses information form the sensors to decide which commands to send
to the FICM, the actuators, and the glow plug system.
The PCM sends a Vref of 5.0 volts to the engine sensors except for CMP and
CKP which generate voltage through the collapse of a magnetic field.
The PCM uses 5 volts as the reference voltage to maintain consistency
throughout all operating conditions.
The Vref is conditioned by the sensors then returned to the PCM for use in
determining the fueling strategy.
AP (Accelerator Pedal Position)
The AP (Accelerator Pedal) is a three track pedal. The AP incorporates
three potentiometers. Throughout the movement of the AP, the resistance
values of the three potentiometers must agree. During the movement of the
AP, if one of the three potentiometer readings do not agree, the check engine
light will illuminate and the vehicle will continue to perform as normal.
If two signals from the AP are lost, the PCM will allow the engine to idle only
and illuminate the check engine light.
The three-track pedal is a safety feature. The three-track pedal takes
the place of the Idle Validation Switch allowing for limited system failure and
still maintaining performance.
Baro (Barometric Pressure)
The BP sensor is a three (3) wire variable capacitance sensor.
The PCM supplies a 5 volt reference signal which the BP sensor uses to
produce a linear analog voltage signal that indicates pressure.
The primary function of the BP sensor is to provide altitude information so
that the PCM can adjust timing, fuel quantity, glow plug on time, and VGT
CKP (Crankshaft Position)
The crankshaft position signal source is a magnetic pickup sensor mounted in
the right front side of the engine block.
The sensor reacts to a target wheel positioned on the crankshaft. The
target wheel is a 60 minus 2 tooth steel disk with 58 evenly spaced teeth and a
slot that's width is equivalent to removing 2 teeth (minus 2 slot) that is the
The sensor will produce pulses for each tooth edge that breaks the magnetic
field created by the permanent magnet that is in the end of the sensor.
Crankshaft speed is derived from the frequency of the CKP sensor signal.
Crankshaft position can be determined by the synchronization of the CKP peg
signal to the CKP minus 2 slot signal.
Diagnostic information on the CKP input signal is obtained by performing
accuracy checks on frequency and/or duty cycle with software strategies.
The PCM needs both the CKP and CMP signal to calculate engine speed and
position. The CKP creates a signal that relates to crankshaft speed and
position relative to TDC (Top Dead Center). The CMP creates a signal
relative to which stroke the piston is currently on (compression or exhaust).
CMP (Camshaft Position)
The camshaft position signal source is a magnetic pickup sensor mounted on
the left front side of the engine block.
The sensor reacts to a peg, pressed into the camshaft at the front of the
The peg will pass the sensor once per camshaft revolution; the sensor will
produce a single pulse correspondingly.
Camshaft speed is derived from the frequency of the CMP sensor signal.
Diagnostic information on the CMP input signal is obtained by performing
accuracy checks on signal levels, frequency, and/or duty cycle with software
The PCM needs both CKP and CMP signals to calculate engine speed and
position. The CMP creates a signal that the PCM uses to indicate a
The CMP contains a permanent magnet which creates a magnetic field, when the
magnetic field is broken by the peg on the camshaft a signal is created.
A conditioned CMPO (Camshaft Position Output) is sent from the PCM to the
FICM so that the FICM can perform fueling calculations.
The PCM conditions the signal and sends it out as TACH signal for body
ECT (Engine Coolant Temp.)
The ECT sensor is a two (2) wire thermistor sensor.
The PCM supplies a 5 volt reference signal which the ECT sensor uses to
produce an analog voltage.
The ECT sensor changes resistance when exposed to different temperatures.
When the temperature of the coolant decreases, the resistance of the
thermistor increases and the signal voltage increases.
When the temperature of the coolant increases, the resistance of the
thermistor decreases and the signal voltage decreases.
EGRVP (Exhaust Gas Recirculation Valve Position)
The EGRVP sensor is a three (3) wire potentiometer type sensor.
The PCM supplies a 5 volt reference voltage that the EGRVP uses to produce a
linear analog voltage that indicates the amount of movement of the valve.
The PCM monitors EGRP as the engine is operating to modulate the EGR valve.
This is a closed loop function which means that the PCM continuously
monitors the EGRVP to ensure proper valve operation.
EOP (Engine Oil Pressure Switch)
The EOP (Engine Oil Pressure Switch) is a switch that closes a circuit to
ground after engine oil pressure reaches approximately 5-7 psi.
This switch controls the oil pressure gauge on the instrument panel.
When pressure is above 7 psi, the gauge will read normal and if the pressure
drops below 6 psi, the gauge will show 0.
The information from the switch is not fed back to the PCM in any way and is
to used as a reference only.
EOT (Engine Oil Temperature)
The EOT sensor is a two (2) wire thermistor type sensor.
The PCM supplies a 5 volt reference signal which the EOT sensor uses to
produce an analog voltage that indicates temperature.
The PCM monitors engine oil temperature via the EOT sensor signal to control
EGR, glow plugs, VGT, and fuel quantity and timing throughout the operating
range of the engine.
The EOT signal allows the PCM to compensate for oil viscosity variations due
to temperature changes in the operating environment, ensuring adequate power and
torque are available for all operating conditions.
EP (Exhaust Pressure)
The EP sensor is a three (3) wire variable capacitance sensor.
The PCM supplies a 5 volt reference signal which the EP sensor uses to
produce a linear analog voltage that indicates pressure.
The EP measures exhaust back pressure so that the PCM can control the VGT
and EGR system.
IAT1 (Intake Air Temperature #1)
The Intake Air Temperature 1 (IAT1) sensor is a two (2) wire thermistor
sensor that is located inside the Mass Air Flow (MAF) sensor.
The PCM supplies a 5 volt reference signal which the IAT1 uses to produce an
analog voltage that indicates the intake air temperature.
The IAT1 sensor's primary function is to measure intake air temperature to
control the timing and fuel rate when cold starting. The continuous
monitoring by the IAT1 sensor limits smoke emissions.
The MAF/IAT1 sensor is mounted in the intake air piping after the air
IAT2 (Intake Air Temperature #2
The IAT2 sensor is a two (2) wire thermistor type sensor.
The IAT2 sensor changes resistance when exposed to different air
When temperature decreases, the resistance of the thermistor increases.
This causes the signal voltage to increase.
When the temperature increases, the resistance of the thermistor decreases.
This causes the signal voltage to decrease.
The primary function of the IAT2 sensor is to provide a feedback signal to
the PCM indicating manifold air temperature.
The PCM supplies a 5 volt reference signal which the IAT2 sensor uses to
produce an analog voltage that indicates temperature.
The PCM monitors the IAT2 signal to determine if the temperature is
During engine operation, if the PCM recognizes that the IAT2 signal is lower
or higher than the expected value, it will set a Diagnostic Trouble Code (DTC)
and illuminate the amber malfunction indicator lamp on the dash.
ICP (Injection Control Pressure)
The ICP sensor is a three (3) wire variable capacitance sensor.
The PCM supplies a 5 volt reference signal which the ICP sensor uses to
produce a linear analog voltage that indicates pressure.
The primary function of the ICP sensor is to provide a feedback signal to
the PCM indicating ICP.
The PCM monitors ICP as the engine is operating to modulate the IPR.
This is a closed loop function which means the PCM continuously monitors and
adjusts for ideal ICP determined by conditions such as load, speed, and
The PCM monitors the ICP signal to determine if the performance of the
hydraulic system is satisfactory.
During engine operation, if the PCM recognizes that the ICP signal is lower
or higher than the value the IPR is trying to achieve, the PCM will set a
Diagnostic Trouble Code (DTC) and illuminate the amber malfunction indicator
lamp on the dash.
The ICP signal from the PCM is one of the signals the FICM uses to command
the correct injection timing.
MAF (Mass Air Flow)
The Mass Air Flow (MAF) sensor uses a hot wire sensing element to measure
the amount of air entering the engine. Air passing over the hot wire
causes it to cool. This hot wire is maintained at 200°C (392°F) above
ambient temperature as measured by a constant cold wire.
The current required to maintain the temperature of the hot wire is
proportional to the air mass flow.
The MAF sensor then outputs an analog voltage signal to the PCM proportional
to the air mass.
MAP (Manifold Absolute Pressure)
The MAP sensor is a three (3) wire variable capacitance sensor.
The PCM uses the MAP sensor signal to assist in the calculation of EGR duty
The PCM measures the MAP signal to determine intake manifold (boost)
Actuators convert electrical output from the PCM to hydraulic, mechanical,
or electronic work.
The 6.0L Power Stroke uses four (4) actuators: Injection Pressure Regulator,
Exhaust Gas Recirculation Valve, Variable Geometry Turbocharger Control Valve,
and Glow Plug Control module.
IPR (Injection Pressure Regulator)
The IPR (Injection Pressure Regulator) is a duty cycle controlled valve that
the PCM uses to control ICP (Injection Control Pressure).
The IPR is a valve that blocks the path to drain for oil coming out from the
high pressure pump. As duty cycle signal increases at the IPR, the
restriction to drain increases, thus increasing ICP.
When the valve is disconnected, it is in its open or drain state and the
engine should not start.
The IPR valve also contains the pressure relief valve for the high pressure
EGR (Exhaust Gas Recirculation
The EGR (Exhaust Gas Recirculation) valve is used to mix cooled exhaust
gasses with intake air to lower emissions and noise.
The EGR valve is duty cycle controlled; the higher the duty cycle, the more
the valve opens.
When the valve is disconnected, it is in its closed state.
VGTCV (Variable Geometry Turbocharger Control Valve)
The VGTCV (Variable Geometry Turbocharger Control Valve) is a duty cycle
controlled valve that directs oil flow to the piston that controls the vanes in
The valve controls pressure to both the open and close side of the piston.
If the valve is disconnected, the turbocharger vanes will remain in a open
Other Electrical Components
Other electrical system compounds include the FICM, PCM, and the glow plug
FICM (Fuel Injection Control Module)
The FICM (Fuel Injection Control Module) receives information from the PCM
(like volume of fuel desired, RPM, EOT, ICP, and others) and uses those signals
to calculate injector start of injection and duration.
After calculating injector fuel delivery timer the IDM sends a 48 volt 20
amp pulse to the correct injector so that the correct amount of fuel will be
delivered to the cylinder at the correct time.
PCM (Powertrain Control Module)
The Powertrain Control Module (PCM), which is mounted behind the battery on
the drivers side inner fender panel, uses sensor inputs to control actuators and
send fueling commands to the FICM.
The PCM controls the fuel and air management systems on the 6.0L Power
Glow Plug System
The glow plug system is used to warm the air in the cylinders to enhance
cold weather startability and reduce start up smoke.
The glow plug system is PCM-controlled.
GPCM (Glow Plug Control Module)
The GPCM (Glow Plug Control Module) is a unit that controls the glow plugs
in order to warm the air in the cylinders.
The GPCM uses a glow plug enable signal to turn the glow plugs on for a time
controlled by the PCM.
The GPCM is capable of diagnosing a problem with one glow plug and then
sending a diagnostic signal to the PCM.
It also has the ability to turn off one glow plug is a short is detected in
The glow plug is used to heat the air in the cylinder.
Inside the plug are two (2) coils (resistance) connected in series; one to
create heat and one to control heat at its peak.
Glow Plug Sleeve
The glow plug sleeve is used to protect the glow plug from engine coolant
and is made of stainless steel.
Glow Plug Buss Bar
Each bank of glow plugs is connected to the wiring harness via a glow plug
The glow plug buss bar has four connectors attached to a single metal rail.
The entire rail must removed to gain access to any of the glow plugs on that
Glow Plug System Diagnostics
One way to verify diagnostic data from the GPCM is to measure the amperage
draw with an inductive amp probe.
Once the glow plug system has been commanded on by the PCM (when engine
temperature is warm you may need to trick the system into a cold condition) for
about 40 sec., the glow plug amperage should be stable. Each glow plug
should draw between 10-12 amps.
When testing the glow plug system, it is best to measure one bank of glow
plugs at a time. The bank with the lower current draw would be the bank
with the bad glow plug and/pr wiring concerns.
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