C27 Petroleum Generator Set Engines Caterpillar

Use this procedure to troubleshoot any suspect problems with the circuit for the coolant level sensor.

The coolant level sensor monitors the engine coolant level in order to warn the operator when the coolant level is low.

Illustration 1	g01150024
Components of the coolant level sensor (1) Sensor (2) Sensor probe (brass dowel) (3) Outer coating

When the probe is not immersed in coolant, approximately +5 VDC is sourced to the sensor signal wire. When this condition is detected by the Electronic Control Module (ECM), a diagnostic code is activated.

Prior to troubleshooting any problems with the coolant level sensor, use Caterpillar Electronic Technician (ET) to check the installation status for the sensor. The coolant level sensors configuration parameter must be set to "Installed" in order for the ECM to monitor the signal from the sensor.

The activation of a diagnostic code and/or a warning lamp is probably caused by a low coolant level. The next likely cause is a problem with the wiring harness, a connector, or the sensor.

Illustration 2	g02167633
Schematic for the coolant level sensor

Test Step 1. Check the Coolant Level

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Pressurized System: Hot coolant can cause serious burns. To open the cooling system filler cap, stop the engine and wait until the cooling system components are cool. Loosen the cooling system pressure cap slowly in order to relieve the pressure.

1. Remove electrical power from the ECM.

   Note: Allow the engine to cool prior to removal of the cooling system pressure cap.

2. Check the coolant level. Refer to the Operation and Maintenance Manual for the proper procedure to check the coolant level.

Results:

• OK - The coolant is at the proper level. Proceed to Test Step 2.

• Not OK - The coolant level is low.

  Repair: Add coolant according to the procedure in the Operation and Maintenance Manual.

  There may be a leak in the cooling system. Identify the source of the coolant leak. Repair the leak. Refer to Systems Operation/Testing and Adjusting, "Cooling System" for additional information.

  STOP

Test Step 2. Verify that the "Coolant Level Sensor" Parameter is Programmed Correctly

1. Connect Cat ET to the service tool connector.

2. Establish communication with the ECM.

3. Verify that the "Coolant Level Sensor" parameter is programmed to "Installed".

4. Remove electrical power from the ECM.

Results:

• The "Coolant Level Sensor" parameter is programmed correctly. - Proceed to Test Step 3.

• The "Coolant Level Sensor" parameter is not programmed correctly. -

  Repair: Program the "Coolant Level Sensor" parameter to "Installed".

  Verify that the repair eliminates the problem.

  STOP

Test Step 3. Check the Supply Voltage at the Sensor Connector

Illustration 3	g02090761
Terminal locations at the harness connector for the coolant level sensor (Terminal A) Sensor supply (Terminal B) Sensor return (Terminal C) Sensor signal

1. Disconnect the coolant level sensor at the sensor connector.

2. Restore electrical power to the ECM.

3. Measure the voltage between terminals A (sensor supply) and B (sensor return) at the harness connector for the coolant level sensor.

4. Remove electrical power from the ECM.

Results:

• The voltage measurement is 8.0 ± 0.5 VDC. - The supply voltage is reaching the sensor. Proceed to Test Step 4.

• The voltage measurement is not 8.0 ± 0.5 VDC. -

  Repair: The sensor supply voltage is not reaching the sensor. There is a problem in the circuit for the sensor supply. Repair the wiring between the sensor and the ECM.

  STOP

Test Step 4. Short the Signal Wire to Ground and Monitor the Status for "Coolant Level"

1. Fabricate a jumper wire that is long enough to create a short circuit between two terminals at the coolant level sensors harness connector. Crimp connector pins to each end of the jumper wire.

2. Install the jumper wire between terminals B (sensor return) and C (sensor signal) on the harness side of the connector for the coolant level sensor.

3. Restore electrical power to the ECM.

4. Monitor the status of "Coolant Level" on Cat ET while the jumper wire is installed.

   Note: Wait at least 30 seconds for activation of the status indicator.

5. Remove the jumper wire. Connect the harness connector for the coolant level sensor.

Results:

• The status changes from "LOW" to "OK" when the jumper wire is installed. The ECM and the wiring harness to the coolant level sensor are OK. -

  Repair: Replace the coolant level sensor.

  Verify that the repair eliminates the problem.

  STOP

• The status does not change from "LOW" to "OK" when the jumper wire is installed. -

  Repair: The problem is between the ECM and the sensor connector. Repair the wiring.

  Verify that the repair eliminates the problem.

  STOP