PLATE AS 3967031 - Caterpillar

The following conditions must exist before any of the above codes will become active:
There are no active 3509 (262) codes.
There are no active 168 codes.The following background information is related to this procedure: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 VoltageThe 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.
Illustration 1 g06272280
Schematic for the active sensors
Illustration 2 g03374231
Fuel rail pressure sensor
(1) Ground
(2) Signal
(3) 5 VDC Supply
Illustration 3 g01170310
Typical example of an engine pressure sensor
(1) 5 VDC Supply
(2) Ground
(3) Signal
Illustration 4 g06272948
DPF inlet temperature sensor
(1) 5 VDC Supply
(2) Ground
(3) Signal
(4) No connection
Table 2
Troubleshooting Test Steps Values Results
1. Check for Diagnostic Codes
A. Establish communication between