C15 and C18 Engines for Caterpillar Built Machines Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with the sensors. Use this procedure if any of the diagnostic codes in Table 1 are active or easily repeated.

Table 1

Diagnostic Codes Table
CDL Code	J1939 Code	Code Description	Comments
100-3	100-3	Engine Oil Pressure Sensor : Voltage Above Normal	The ECM detects signal voltage that is not in the acceptable range. The code is logged. The value of the parameter is set to a gauge pressure.
100-4	100-4	Engine Oil Pressure Sensor : Voltage Below Normal	The ECM detects signal voltage that is not in the acceptable range. The code is logged. The value of the parameter is set to a gauge pressure.
274-3	108-3	Atmospheric Pressure Sensor : Voltage Above Normal	The ECM detects signal voltage that is not in the acceptable range. The code is logged. The value of the parameter is set to a gauge pressure.
274-4	108-4	Atmospheric Pressure Sensor : Voltage Below Normal	The ECM detects signal voltage that is not in the acceptable range. The code is logged. The value of the parameter is set to a gauge pressure.
460-3	5580-3	Fuel Pressure Sensor - After Fuel Filter : Voltage Above Normal	The ECM detects signal voltage that is not in the acceptable range. The code is logged. The value of the parameter is set to a gauge pressure.
460-4	5580-4	Fuel Pressure Sensor - After Fuel Filter : Voltage Below Normal	The ECM detects signal voltage that is not in the acceptable range. The code is logged. The value of the parameter is set to a gauge pressure.
1785-3	3563-3	Intake Manifold Pressure Sensor : Voltage Above Normal	The ECM detects signal voltage that is not in the acceptable range. The code is logged. The value of the parameter is set to a gauge pressure.
1785-4	3563-4	Intake Manifold Pressure Sensor : Voltage Below Normal	The ECM detects signal voltage that is not in the acceptable range. The code is logged. The value of the parameter is set to a gauge pressure.
2738-3	1176-3	Turbocharger #1 Compressor Inlet Pressure Sensor : Voltage Above Normal	The ECM detects signal voltage that is not in the acceptable range. The code is logged. The value of the parameter is set to a gauge pressure.
2738-4	1176-4	Turbocharger #1 Compressor Inlet Pressure Sensor : Voltage Below Normal	The ECM detects signal voltage that is not in the acceptable range. The code is logged. The value of the parameter is set to a gauge pressure.

The supply voltage is routed to terminal 1 of each sensor connector. The sensor return is routed to terminal 2 of each sensor connector. The sensor signal is routed to terminal 3 of each sensor connector. The ECM provides short circuit protection for the internal power supply. A short circuit to the battery will not damage the internal power supply.

Diagnostics on the Caterpillar Electronic Technician (ET)

WIGGLE TEST - The Wiggle Test allows you to monitor the status of the signals from the sensors.

For additional information regarding the Wiggle Test, refer to the documentation that accompanies the Cat ET software.

Illustration 1	g03019883

Note: The diagram above is a simplified schematic of the electrical circuit. The schematic is electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision of the Electrical Schematic for the complete schematic.

Table 2

Troubleshooting Test Steps	Values	Results
1. Check for Diagnostic Codes A. Establish communication between Caterpillar Electronic Technician (ET) and the ECM . Refer to Troubleshooting, "Electronic Service Tools", if necessary. B. Turn the keyswitch to the ON position. C. Look for a "-3"," -4", or "-10" active or logged codes:	Diagnostic code	Result: A -3 diagnostic code is active. Proceed to Test Step 2. Result: A -4 diagnostic code is active. Proceed to Test Step 3. A-10 diagnostic code is active. A 10 diagnostic code indicates an open in the voltage supply to a sensor. If the code is only present for one sensor, the open will be between the sensor connector and a splice. If the open is for two or more sensors, the open will be before the splice for the voltage supply to those sensors. Repair the open in the wiring or connectors. Refer to the electrical schematic for the locations of splices in the harness.
2. Create a Short at the Sensor Connector A. Use a test lamp in order to create a short between terminal 3 (signal) and terminal 2 (sensor return) at the sensor connector. B. Turn the keyswitch to the ON position. C. Monitor the diagnostic codes on Cat ET. Check for an active -4 diagnostic code for the suspect sensor. D. Turn the keyswitch to the OFF position.	Short created	Result: A -4 diagnostic code became active after creating the short at the sensor connector. The wiring is OK. Replace the sensor. Verify that the problem is resolved. Result: A -4 diagnostic code does not become active for the suspect sensor. Proceed to Test Step 4.
3. Create an Open at the Suspect Sensor Connector A. Turn the keyswitch to the OFF position. B. Disconnect the sensor connector of the suspect sensor with the active -4 diagnostic code. C. Turn the keyswitch to the ON position. D. Monitor the diagnostic codes on Cat ET. Check for an active -3 diagnostic code for the suspect sensor. E. Turn the keyswitch to the OFF position.	Create an Open	Result: A -3 diagnostic code became active after disconnecting the sensor. The wiring is OK. Replace the sensor. Verify that the problem is resolved. Result: A -3 diagnostic code did not became active after disconnecting the sensor. Proceed to Test Step 4.
4. Check the 5 VDC Supply Voltage at the Sensor Connector A. Turn the keyswitch to the ON position. B. Measure the voltage between pin 1 and pin 2 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 5 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. STOP
5. Perform the Wiggle Test Carefully following this procedure is the best way to identify the root cause of an intermittent problem. A. Turn the keyswitch to the ON position. B. Use CAT ET to run the "Wiggle Test". C. Slowly wiggle the wiring and the connectors between the P2 connector and the sensor. Pay particular attention to the wiring near each connector. Be sure to wiggle all of the wiring. As you wiggle the wiring look for these problems. 1. Loose connectors or damaged connectors 2. Moisture on the connectors or the wiring 3. Damaged that is caused by excessive heat 4. Damage that is caused by chafing 5. Improper routing of wiring 6. Damaged insulation	Test passed	Result: The wiring failed the Wiggle Test. There is a problem with the wiring. Repair the wiring or replace the wiring. Verify that the problem is resolved. STOP Result: The wiring passed the Wiggle Test. The problem may be intermittent. Inspect the wiring. Refer to Troubleshooting, "Electrical Connectors - Inspect". If the wiring looks OK perform the following procedure. 1. Turn the keyswitch to the OFF position. 2. Disconnect the connectors. Carefully inspect the terminals for proper installation. Make sure that each terminal is clean and dry. 3. Insert a pin into each socket. Verify that each socket grips the pin firmly. Repair any problems. 4. Connect all connectors. 5. Verify that the problem is resolved. 6. Return the unit to service. STOP

Complete the procedure in the order in which the steps are listed.

If the procedure corrected the issue, return the engine to service.

If the procedure did not correct the issue, Contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).