PLUNGER 6E0757 - Caterpillar

The following conditions must exist before any of the above codes will become active:
There are no active 3509 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 g06274072
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
Table 2
Troubleshooting Test Steps Values Results
1. Check for Diagnostic Codes
A. Establish communication between the electronic service tool and the ECM . Refer to Troubleshooting, "Electronic Service Tools", if necessary.
B. Turn the keyswitch to the ON position.
C. Look for a -3, or -4 active or logged codes:
Diagnostic code
Result: There are no active diagnostic codes for the active sensors.
Repair: If there are logged diagnostic codes for the active sensors, the fault may be intermittent.
Refer to Troubleshooting, "Electrical Connectors - Inspect" to identify intermittent faults.
Result: A diagnostic code that is listed in Table 1is active.
Proceed to Test Step 2.
2. Check the 5 VDC Supply Voltage at the Sensor Connector
A. Turn the keyswitch to the ON position.
B. Measure the voltage between the sensor supply pin and the sensor return pin at the suspect sensor.
Test passed
Result: The supply voltage is approximately 5.0 0.2 VDC
Connect the sensor and then proceed to Test Step 3.
Result: The supply voltage is not approximately 5.0 0.2 VDC.
There is a short in the harness to the battery. Repair the wiring or replace the harness
Verify that the problem is resolved.
3. Check the Type of Diagnostic Code that is Active
A. Turn the keyswitch to the ON position. Wait at least 10 seconds for activation of the diagnostic codes.
B. Use the electronic service tool to check for active diagnostic codes. Record all active diagnostic codes.
Diagnostic