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

Illustration 1	g00596060
Schematic For Temperature Sensor (Engine Coolant)

The EMCP II monitors the engine coolant temperature in order to protect the engine in case of a problem with the coolant temperature. The temperature sensor is mounted in the water jacket toward the front of the engine. The exact location of the engine coolant temperature sensor depends on the engine model.

The sensor is powered by an 8 volt sensor supply from the GSC. The coolant temperature signal is a pulse width modulated signal. The base frequency of the signal is 455 ± 90 Hz. As temperature changes, the duty cycle of the signal varies from 10% to 95%. A temperature of -40 °C (-40 °F) is approximately 10% of the duty cycle. A temperature of 135 °C (275 °F) is approximately 93% of the duty cycle.

Note: The GSC is usually programmed to treat a diagnostic code with the temperature sensor as an alarm fault (P04 = 0). If the GSC is programmed to treat a fault with the temperature 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 -battery of the sensor signal.

Begin performing these procedures only when CID 110 FMI 4 is showing and the "DIAG" indicator is FLASHING on the upper display. The GSC treats a CID 110 FMI 4 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 GSC and the harness.

   1. Ensure that CID 110 FMI 4 is showing on the display.

   2. Turn the ECS to the "OFF/RESET" position.

   3. Disconnect the sensor from the engine harness. The sensor should remain fastened to the engine.

   4. Turn the ECS to the "STOP" position.

   5. Press the alarm codes key. This is not required for shutdown faults.

   6. Verify that CID 110 FMI 4 is no longer showing and verify that CID 110 FMI 3 is now showing.

      Expected Result: CID 110 FMI 4 is not showing. CID 110 FMI 3 is now showing.

      Results:

      • OK - The GSC and the harness function properly. Therefore, the sensor is faulty. Replace the sensor. STOP.

      • NOT OK - CID 110 FMI 4 is still showing. There is a fault in the GSC or the harness. Proceed to 2.

2. Check the GSC.

   1. Turn the ECS to the "OFF/RESET" position.

   2. Disconnect the harness connector from the GSC.

   3. Turn the ECS to the "STOP" position.

   4. Press the alarm codes key.

   5. Verify that CID 110 FMI 4 is no longer showing and verify that CID 110 FMI 3 is now showing.

      Expected Result: CID 110 FMI 4 is not showing. CID 110 FMI 3 is now showing.

      Results:

      • OK - The GSC functions properly. Therefore, the signal wire is faulty in the harness. Troubleshoot the signal wire in the harness between the sensor connector and the GSC connector. Also check the electrical connectors and terminals. See Testing and Adjusting, "Electrical Connector - Inspect". STOP.

      • NOT OK - CID 110 FMI 4 is still showing. The GSC is faulty. Replace the GSC. See Testing and Adjusting, "EMCP Electronic Control (Generator Set) - Replace".