Navistar International DT 466 Diagnostic/Troubleshooting Manual page 53

• EFP
• EOP
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 three wires:
• V
REF
• Signal return
• Signal ground
The sensor receives the V
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.
Barometric Absolute Pressure (BAP)
The ECM monitors the BAP signal to determine
altitude, adjust timing, fuel quantity, and inlet air
heater operation. The BAP sensor is located in the
cab.
Manifold Absolute Pressure (MAP)
The ECM monitors the MAP signal to determine intake
manifold pressure (boost). This information is used
to control fuel rate and injection timing. The MAP
sensor is installed left of the MAT sensor in the intake
manifold.
Engine Oil Pressure (EOP)
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 and left of the fuel filter
housing.
Exhaust Back Pressure (EBP)
The EBP sensor measures exhaust back pressure
so that the ECM can control the VGT and EGR
systems. The sensor provides feedback to the ECM
for closed loop control of the Variable Geometry
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
1 ENGINE SYSTEMS
and returns an analog
REF
EGES-270-1
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
Turbocharger (VGT). The EBP sensor is installed
in a bracket mounted on the water supply housing
(Freon® compressor bracket).
Engine Fuel Pressure (EFP)
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 rear of the fuel filter assembly
(crankcase side).
Figure 41 Micro Strain Gauge sensor
1. Pressure sensor
2. Electronic Control Module (ECM)
3. Ground
4. Microprocessor
5. Voltage reference (V
Micro Strain Gauge (MSG) Sensors
• BCP
• ICP
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 three wires:
• V
REF
• Signal return
• Signal ground
)
REF
49