The 5 VDC sensor supply provides power to all 5
VDC sensors. The ECM supplies 5 VDC to terminal
“3” of the fuel rail pressure sensor connector and to
terminal “1” of all other active sensor connectors. The
sensor common from the ECM connector goes to
terminal “1” of the connector for the fuel rail pressure
sensor. The sensor common from the ECM
connector goes to terminal “2” of all other active
sensor connectors. The sensor supply is output short
circuit protected. A short circuit to the battery will not
damage the circuit inside the ECM.
Pull-up Voltage
The ECM continuously outputs a pull-up voltage on
the circuit for the sensor signal wire. The ECM uses
this pull-up voltage to detect an open in the signal
circuit. When the ECM detects a voltage above a
threshold on the signal circuit, an open circuit
diagnostic code (XXXX-3) is generated for the
sensor.
If the sensor is disconnected, pull-up voltage
indicates that the wires from the sensor connector to
the ECM are not open or shorted to ground. If the
sensor is disconnected, the absence of pull-up
voltage indicates an open in the signal wire or a short
to ground. If the sensor is disconnected and the
voltage is different from pull-up voltage, the signal
wire is shorted to another wire in the harness.
384 UENR4469-36
Circuit Tests
Copyright of Perkins Engine Company Limited. NOT FOR REPRINTING OR RESALE
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