1.18.8. STE/ICE and Diagnostic Connector Circuit.
The STE/ICE and diagnostic connector circuit consists of
tachometer generator, temperature sensor, and current
The diagnostic connector assembly (DCA box) contains
the electrical connector to mate the paving machine
diagnostic sensors with the STE/ICE Vehicle Test Meter
(VTM). The DCA box provides the power for the test set.
Within the DCA box is the vehicle identification code
resistor to identify to the vehicle test meter the type of
internal combustion engine being tested. The DCA box
contains two toggle switches. The ENGINE CRANK
switch disables the engine fuel shutoff solenoid to
prevent the engine from starting during certain tests.
The ZERO OFFSET switch is used during engine
coolant temperature tests to set the sensor to zero. 24
VDC from the paving machine is sent to the DCA
connector on the DCA box for power for the vehicle test
Four pressure transmitters are used on the paving
machine to check engine fuel pressure, engine oil
pressure, turbosupercharger outlet pressure, and air
cleaner outlet pressure. These sensors are as follows:
Fuel and oil pressure transmitters measure the
engine fuel lift pump and engine oil pump outlet
transmitter measures the discharge pressure of
The air cleaner pressure transmitter measures
air cleaner outlet pressure in respect to the
ambient air pressure.
Two differential pressure switches are used to measure
the restriction of engine fuel and engine oil through the
filters. This is used to determine if the filters are clogged
or need changing. The pressure difference will display
as a PASS/FAIL indication.
The tachometer generator used to measure engine
speed is a pulse detector. The detector is mounted on
the timing gear cover and is driven by the timing gears.
Engine speed is measured as a series of pulses through
the timing gears.
The engine coolant temperature transducer is a resistive
temperature sensor installed on the engine near the
thermostat housing. It measures the engine coolant
Engine current measurements are made using a current
shunt. Starter tests and battery resistance tests use the
current shunt as a detector.
Resistance tests are performed by the voltage test
meter. These consist of battery internal resistance,
starter circuit resistance, and battery resistance change.
Voltage measurements are performed by the voltage test
meter. These consist of starter voltage during cranking,
alternator output voltage, and alternator field voltage.
DIAGNOSTICS CONNECTOR ASSEMBLY