3126B and 3126E On-highway Engines Caterpillar

The ECM detects the following conditions:

• The engine oil pressure is below the trip line in Illustration 1 for more than eight seconds.

Illustration 1	g00821786
Very low oil pressure

System Response:

The Caterpillar Electronic Technician (Cat ET) will display "LOW OIL PRESSURE" and "DIAG" next to the status for "Engine Oil Pressure". The check engine lamp and the warning lamp will illuminate.

Customer passwords are required to clear this diagnostic code.

The ECM will use the default torque map. The engine speed is limited to 1350 RPM and the vehicle speed is limited to 72 km/h (45 mph).

Note: If the "Engine Monitoring" parameter is programmed to "Shutdown", the engine will be shutdown after this code has been active for 30 seconds.

Note: If "Engine Monitoring" is programmed to "Warning" the engine power will not be affected.

Test Step 1. Check the Engine Oil Level

1. Check the engine oil level.

Expected Result:

The engine oil level is OK.

Results:

• OK - The engine oil level is OK. Proceed to Test Step 2.

• Not OK - The engine oil level is low.

  Repair: Add engine oil to the proper level. Refer to the Operation and Maintenance Manual for more information.

  STOP

Test Step 2. Verify Proper Sensor Installation

1. Check the installation of the engine oil pressure sensor.

2. Check the wiring of the engine oil pressure sensor. Refer to the Electrical Schematic for the proper wiring. Ensure that all of the wires and connectors are properly connected.

Expected Result:

The sensor is properly installed and the wiring is correct.

Results:

• OK - The sensor is properly installed. Proceed to Test Step 3.

• Not OK - The sensor is not installed properly.

  Repair: Install the engine oil pressure sensor properly. Repair the wiring and/or the connectors to the sensor.Verify that the repair eliminates the problem.

  STOP

Test Step 3. Check for Active Diagnostic Codes

1. Connect Cat ET to the data link connector.

2. Check for active diagnostic codes that are related to the barometric pressure sensor (atmospheric pressure) or the boost pressure sensor.

Expected Result:

There are no diagnostic codes that are related to the barometric pressure sensor (atmospheric pressure) or the boost pressure sensor.

Results:

• OK - There are no diagnostic codes. Proceed to Test Step 4.

• Not OK - There is a diagnostic code that is related to the barometric pressure sensor (atmospheric pressure) and/or the boost pressure sensor.

  Repair: Troubleshoot the diagnostic code before continuing with this procedure.

  STOP

Test Step 4. Check the Status Screen

1. Turn the key switch to the ON position. The engine should be off.

2. Monitor the status for "Boost Pressure" and "Engine Oil Pressure" on Cat ET.

Expected Result:

"Boost Pressure" and "Engine Oil Pressure" should be less than 10 kPa (2 psi).

Results:

• OK - The boost pressure and the engine oil pressure are less than 10 kPa (2 psi). Proceed to Test Step 6.

• Not OK - Boost Pressure - The boost pressure is greater than 10 kPa (2 psi). Proceed to Test Step 8.

• Not OK - Engine Oil Pressure - The engine oil pressure is greater than 10 kPa (2 psi). Proceed to Test Step 9.

• Not OK - Both - The boost pressure and the engine oil pressure are greater than 10 kPa (2 psi). Proceed to Test Step 5.

Test Step 5. Check the Supply Voltage to the Pressure Sensors

1. Disconnect the barometric pressure sensor (atmospheric pressure), the boost pressure sensor, and the engine oil pressure sensor.

2. Turn the key switch to the ON position.

3. Measure the voltage between terminal A (Engine Pressure Sensor +5V) and terminal B (Engine Pressure Sensor Common) of each pressure sensor connector on the engine harness.

Expected Result:

The voltage is 5.0 ± 0.16 VDC.

Results:

• OK - The voltage is within the range.

  Repair: Reconnect the engine oil pressure sensor and the boost pressure sensor.Temporarily connect a new barometric pressure sensor (atmospheric pressure).If the new sensor fixes the problem, reconnect the suspect sensor.If the problem returns, permanently replace the sensor.Verify that the repair eliminates the problem.

  STOP

• Not OK - There is a problem with the 5 volt supply.

  Repair: Check the J2/P2 ECM connector and the sensor connectors for corrosion and moisture.Check the 5 volt supply wire. Verify that the wire is not cut and that the wire is completely inserted into the connectors for the pressure sensors on the engine harness.Verify that the repair eliminates the problem.

  STOP

Test Step 6. Install a Pressure Gauge

1. Remove the engine oil pressure sensor.

2. Install a 1U-5470 Engine Pressure Group into the oil gallery with a Tee fitting in the port for the engine oil pressure sensor.

3. Connect the engine oil pressure sensor to the Tee fitting.

4. Turn the key switch to the ON position.

5. Monitor the status for "Engine Oil Pressure" on Cat ET.

6. Start the engine and run the engine at low idle.

7. Compare the pressure reading on the gauge to the pressure reading on Cat ET.

8. Monitor the status screen and the gauge while you increase the engine speed.

Expected Result:

The gauge and the status screen are within 35 kPa (5.0 psi) of each other.

Results:

• OK - The sensor is functioning properly. Proceed to Test Step 7.

• Not OK - The sensor is not functioning properly.

  Repair: Temporarily install a new engine oil pressure sensor.If the new sensor repairs the problem, reinstall the suspect sensor.If the problem returns, replace the sensor.Verify that the repair eliminates the problem.

  STOP

Test Step 7. Compare the Readings to the Oil Pressure Map

1. Compare the readings from the pressure gauge to the oil pressure maps in Illustration 1.

Expected Result:

The engine oil pressure is above the trip points in Illustration 1.

Results:

• OK - The engine oil pressure appears to be OK at this time.STOP

• Not OK - The engine oil pressure is lower than the trip line on the oil pressure map. There is a mechanical problem.

  Repair: Refer to Testing and Adjusting, "Engine Oil Pressure - Test".

  STOP

Test Step 8. Check the Supply Voltage to the Boost Pressure Sensor

1. Disconnect the boost pressure sensor.

2. Turn the key switch to the ON position.

3. Measure the voltage between terminal A (Engine Pressure Sensor +5V) and terminal B (Engine Pressure Sensor Common) of the connector for the boost pressure sensor on the engine harness.

Expected Result:

The voltage is 5.0 ± 0.16 VDC.

Results:

• OK - The voltage is within the range.

  Repair: Temporarily connect a new boost pressure sensor.If the new sensor fixes the problem, reconnect the suspect sensor.If the problem returns, permanently replace the sensor.Verify that the repair eliminates the problem.

  STOP

• Not OK - There is a problem with the 5 volt supply.

  Repair: Check the sensor connector for corrosion and moisture.Check the 5 volt supply wire. Verify that the wire is not cut and that the wire is completely inserted into the connector for the boost pressure sensor on the engine harness.Verify that the repair eliminates the problem.

  STOP

Test Step 9. Check the Supply Voltage to the Engine Oil Pressure Sensor

1. Disconnect the engine oil pressure sensor.

2. Turn the key switch to the ON position.

3. Measure the voltage between terminal A (Engine Pressure Sensor +5V) and terminal B (Engine Pressure Sensor Common) of the connector for the engine oil pressure sensor on the engine harness.

Expected Result:

The voltage is 5.0 ± 0.16 VDC.

Results:

• OK - The voltage is within the range.

  Repair: Temporarily connect a new engine oil pressure sensor.If the new sensor fixes the problem, reconnect the suspect sensor.If the problem returns, permanently replace the sensor.Verify that the repair eliminates the problem.

  STOP

• Not OK - There is a problem with the 5 volt supply.

  Repair: Check the sensor connector for corrosion and moisture.Check the 5 volt supply wire. Verify that the wire is not cut and that the wire is completely inserted into the connector for the engine oil pressure sensor on the engine harness.Verify that the repair eliminates the problem.

  STOP