Electronic Modular Control Panel II (EMCP II) For MUI Engines Caterpillar

Illustration 1	g00595836
Schematic For Pressure Sensor (Engine Oil)

The EMCP II monitors the engine oil pressure in order to protect the engine in case of a problem with the oil pressure. The pressure sensor is usually mounted on an oil gallery of the engine. The exact location of the engine oil pressure sensor depends on the engine model.

The sensor is powered by an 8 volt sensor supply from the GSC. The oil pressure signal is a pulse width modulated signal. The base frequency of the signal is 500 ± 150 Hz. As pressure changes, the duty cycle of the signal varies from 10% to 95%. A pressure of 0 kPa (0 psi) is approximately 13% of the duty cycle. A pressure of 690 kPa (100 psi) is approximately 85% of the duty cycle.

Note: The GSC is usually programmed to treat a diagnostic code with the pressure sensor as an alarm fault (P04 = 0). If the GSC is programmed to treat a fault with the pressure sensor as a shutdown fault (P04 = 1), then diagnostic codes are automatically shown on the upper display.

Note: Faults are created when the harness connector (40 contact) is disconnected from the GSC during these troubleshooting procedures. Clear these created faults after the particular fault is corrected. In a properly operating system, when the harness connector is removed from the GSC, the following diagnostic codes are recorded.

• CID 100 FMI 3 pressure sensor (engine oil)

• CID 110 FMI 3 temperature sensor (engine coolant)

• CID 111 FMI 3 fluid level sensor (engine coolant)

• CID 190 FMI 3 speed sensor (engine)

• CID 331 FMI 2 switch (engine control)

• CID 336 FMI 2 switch (engine control)

Procedure

This diagnostic code can be caused by the following conditions:

• There is a short to the +battery of the sensor signal.

• There is an open circuit of the sensor signal.

Begin performing these procedures only when CID 100 FMI 3 is showing and the "DIAG" indicator is FLASHING on the upper display. The GSC treats a CID 100 FMI 3 as an alarm fault. Active alarm faults are shown on the display when the alarm codes key is pressed and the ECS is in any position except the OFF/RESET position. For an inactive fault, the problem may be intermittent. To troubleshoot an inactive fault, use the preceding system schematic and see Testing And Adjusting, "Electrical Connector - Inspect". Clear the diagnostic code from the fault log after troubleshooting is complete.

Note: If CID 269 is active, then correct the diagnostic code prior to proceeding with this procedure.

1. Check the circuit for the supply.

   1. Turn the ECS to OFF/RESET and then turn the ECS to the STOP position.

   2. Disconnect the sensor from the engine harness. The sensor remains fastened to the engine.

   3. At the side of the engine harness on the sensor connector, measure the voltage (DCV) between contact "A" (supply) and contact "B" (sensor ground).

      Expected Result: The voltage should be 8.0 ± 0.5 DCV.

      Results:

      • OK - The supply circuit functions properly. Proceed to 2.

      • NOT OK - The supply circuit is faulty. Check the upper display for a CID 269. If necessary, correct the fault. If a CID 269 is not showing on the upper display, then the engine harness has an open circuit. Proceed to 4.

2. Check the signal circuit.

   The ECS remains in the STOP position and the sensor remains disconnected from the engine harness.

   1. At the side of the engine harness on the sensor connector, measure the voltage (DCV) between contact "C" (signal) and contact "B" (sensor ground).

      Expected Result: The voltage should be 7.0 ± 0.5 DCV.

      Results:

      • OK - The signal circuit functions properly. Verify that the diagnostic code remains present. Reconnect the sensor. Turn the ECS to OFF/RESET and then turn the ECS to STOP. If the CID 100 FMI 3 is still showing on the upper display, the sensor is faulty. Replace the sensor. STOP.

      • NOT OK - Voltage is equal to battery positive (B+). The engine harness is faulty. The signal circuit within the engine harness is shorted to the battery ("B+"). Troubleshoot the engine harness and repair the engine harness. STOP.

      • NOT OK - Voltage is NOT 7.0 ± 0.5 DCV and is NOT equal to battery positive (B+). The GSC or the harness is faulty. Proceed to 3.

3. Check for a shorted harness.

   When you are performing this step, see the preceding System Schematic. The sensor remains disconnected from the engine harness.

   1. Turn the ECS to OFF/RESET.

   2. Disconnect the harness connector from the GSC.

   3. At the GSC harness connector, measure the resistance from signal contact 8 to all other contacts of the connector.

      Expected Result: For each measurement, the resistance should be greater than 5000 ohms.

      Results:

      • OK - The harness functions properly. Proceed to 4.

      • NOT OK - The harness wiring with the incorrect resistance is shorted in the harness. Troubleshoot and repair the faulty harness wiring between the sensor connector and the GSC connector. STOP.

4. Check for an open harness.

   When you are performing this step, see the preceding System Schematic. The ECS remains in the OFF/RESET position. The sensor remains disconnected from the engine harness and the GSC remains disconnected from the harness connector.

   1. Measure the resistance of the ground circuit. Measure the resistance from contact "B" of the sensor harness connector to contact "31" of the GSC harness connector.

   2. Measure the resistance of the signal circuit. Measure the resistance from contact "C" of the sensor harness connector to contact "8" of the GSC harness connector.

   3. Measure the resistance of the sensor supply circuit. Measure the resistance from contact "A" of the sensor harness connector to contact "9" of the GSC harness connector.

      Expected Result: For each measurement, the resistance should be 5 ohms or less.

      Results:

      • OK - The harness functions properly. Proceed to 5.

      • NOT OK - The harness wiring with the incorrect resistance measurement is open (faulty). Troubleshoot and repair the faulty harness wiring between the sensor connector and the GSC connector. STOP.

5. Check the electrical connectors.

   1. Check the electrical connectors, terminals and wiring. See Testing And Adjusting, "Electrical Connector - Inspect".

      Expected Result: All connectors, terminals and wiring should function properly.

      Results:

      • OK - Connect all harness connectors that were previously disconnected. Start the engine. If CID 100 FMI 3 is still showing, replace the GSC. See Testing And Adjusting, "EMCP Electronic Control (Generator Set) - Replace". STOP.

      • NOT OK - Repair the faulty area. STOP.