EDGE AS 5404031 - Caterpillar

The following background information is related to this procedure:The ECM supplies regulated +5 V to the following sensors:
Intake manifold air pressure sensor
Fuel pressure sensor
Engine oil pressure sensorThe ECM supplies regulated +8 V to the following sensors:
Primary speed/timing sensor
Secondary speed/timing sensorNote: Refer to the Electrical Schematic for the application for information regarding components that are connected to the 5 V and 8 V supplies on the J1/P1 connector.A diagnostic code can be caused by the following conditions:
A short circuit in the harness
A short circuit to a voltage that is higher than 5.16 V
A faulty sensor
A faulty ECM
An open circuit in the harness
Illustration 1 g03682449
5 V supply circuit
Illustration 2 g03682459
8 V supply circuit
Note: Refer to the Electrical Schematic for the application for information regarding components that are connected to the 5 V and 8 V supplies on the J1/P1 connector.
Illustration 3 g03375608
P2 pin locations for the sensor supply circuits
(10) 8 V supply
(38) Intake manifold pressure sensor return
(39) Oil pressure sensor return
(40) Fuel rail pressure sensor return
(46) Intake manifold air pressure sensor 5 V supply
(47) Oil pressure sensor 5 V supply
(48) Fuel rail pressure sensor 5 V supply
Illustration 4 g03374231
Fuel rail pressure sensor
(1) Ground
(2) Signal
(3) 5 V Supply
Illustration 5 g01170310
Typical example of an engine pressure sensor
(1) 5 V Supply
(2) Ground
(3) Signal
Illustration 6 g01212995
Typical example of a speed/timing sensor
(1) 8 V supply
(2) Signal
Table 2
Troubleshooting Test Steps Values Results
1. Determine the Code
A. Connect the electronic service tool to the service tool connector. Refer to Troubleshooting, "Electronic Service Tools", if necessary.
B. Turn the keyswitch to the ON position.
C. Determine if a diagnostic trouble code is present.
Diagnostic Codes
Result: A -3 or -4 code is present.
Note which sensor supply has the active diagnostic code.
Proceed to Test Step 2.
2. Check for a Failed Sensor
A. Connect to the electronic service tool.
B. Turn the keyswitch to the ON position.
C. Disconnect a sensor on the suspect sensor supply circuit.
D. Monitor the electronic service tool while the sensor is disconnected to see if the active code changes to logged.
E. Connect the suspect sensor to the wiring harness
F. Repeat steps C through E for each sensor on the suspect sensor supply.
Note: Refer to the Electrical Schematic for the application for information regarding components that are connected to the 5 V and 8 V supplies on the J1/P1 connector.
Failed Sensor
Result: The suspect sensor supply active code changes to logged when a sensor is unplugged.
Repair: Replace the failed sensor.
Verify that the repair resolved the problem.
Result: The suspect sensor supply active code remains active after all sensors on the sensor supply circuit have been checked.
Repair: A failed wiring harness has been detected. Repair or replace the wiring harness.
Verify that the repair resolved the problem.
If the procedure did not correct the fault, contact the Dealer Solutions Network (DSN).