1.18.8. STE/ICE and Diagnostic Connector Circuit.

TM 5-3895-373-20 1.18.8. STE/ICE and Diagnostic Connector Circuit. The STE/ICE and diagnostic connector circuit consists of a diagnostic connector assembly, four pressure transmitters, two pressure differential switches, a tachometer generator, temperature sensor, and current shunt. 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 meter. 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 pressures. The turbosupercharger outlet pressure transmitter measures the discharge pressure of the turbosupercharger. 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 temperature. 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 1-33