3408E and 3412E Industrial Engines Caterpillar

The coolant level sensor provides a means of monitoring the engine coolant level in order to warn the operator in the event that the coolant level is low. The coolant level sensor is usually located in the top tank of the radiator. The sensor should be immersed in coolant at all times.

Illustration 1	g00831580
Schematic

Illustration 2	g00894439
P1 ECM connector

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. Stop the engine.

2. After allowing the engine to cool, check the coolant level. Refer to the Operation and Maintenance Manual for the proper procedure to check the coolant level.

Expected Result:

The coolant should be at the proper 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.Verify that the repair eliminates the problem. Identify the source of the coolant leak and fix the problem.

  Stop.

Test Step 2. Verify that the Coolant Level Sensor is Installed

1. Locate the coolant level sensor on the engine. Verify that a coolant level sensor is installed on the engine.

Expected Result:

The coolant level sensor is installed on the engine.

Results:

• OK - The coolant level sensor is installed on the engine. Proceed to Test Step 3.

• Not OK - The coolant level sensor is not installed.

  Repair: Change the parameter for the coolant level sensor to "Not Installed". Verify that the repair eliminates the problem.

  Stop.

Test Step 3. Inspect Electrical Connectors and Wiring

1. Turn the keyswitch to the OFF/RESET position.

2. Thoroughly inspect the J1/P1 ECM connector, the J3/P3 customer connector, the J34/P34 coolant level sensor connector, and any other connectors in the circuit. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

Expected Result:

All connectors, pins, and sockets should be completely inserted, and coupled. The harness and wiring should be free of corrosion, abrasion, and pinch points.

Results:

• OK - Proceed to Test Step 4.

• Not OK -

  Repair: Repair the circuit.Verify that the repair eliminates the problem.

  Stop.

Test Step 4. Monitor the Status of "Coolant Level"

1. Connect the Caterpillar Electronic Technician (Cat ET) to the service tool connector.

2. Turn the keyswitch to the ON position and monitor the status of "Coolant Level" on Cat ET.

3. Turn the keyswitch to the OFF/RESET position.

Expected Result:

The status should be "OK".

Results:

• OK - The status is "OK". Proceed to Test Step 5.

• Not OK - The status is "Low". Proceed to Test Step 6.

Test Step 5. Disconnect the Coolant Level Sensor and Monitor the Status of "Coolant Level"

1. Disconnect the J34/P34 coolant level sensor connector.

2. Turn the keyswitch to the ON position and monitor the status of "Coolant Level" on Cat ET.

3. Turn the keyswitch to the OFF/RESET position.

Expected Result:

The status should change from "OK" to "Low" when you disconnect the sensor.

Results:

• OK - The status is "Low" when the sensor is disconnected. The coolant level sensor is working properly. Stop.

• Not OK - The status is "OK" when the sensor is disconnected. Proceed to Test Step 7.

Test Step 6. Short the Harness and Monitor the Status of "Coolant Level"

1. Disconnect the J34/P34 coolant level sensor connector.

2. Turn the keyswitch to the ON position and monitor the status of "Coolant Level" on Cat ET.

3. Install a jumper wire between P34:B Digital Sensor Return and P34:C Signal.

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

5. Remove the jumper wire.

6. Turn the keyswitch to the OFF/RESET position.

Expected Result:

The status should change from "Low" to "OK" when you install the jumper wire.

Results:

• OK - The ECM and the wiring to the coolant level sensor are OK.

  Repair: Replace the coolant level sensor.Verify that the repair eliminates the problem.

  Stop.

• Not OK - Shorting the circuit does not affect the status on Cat ET. Proceed to Test Step 7.

Test Step 7. Check for Opens in the Wiring

1. Turn the keyswitch to the OFF/RESET position.

2. Disconnect the J1/P1 ECM connectorand the J34/P34 coolant level sensor connector.

3. Measure the resistance between the following terminals:
   • P1:35 (Digital Sensor +8V) to P34:A (Digital +8V)

   • P1:30 (Analog Sensor Return) to P34:B (Digital Return)

   • P1:24 (Coolant Level Sensor) to P34:C (Signal)

Expected Result:

The resistance should be less than 10 Ohms for each measurement.

Results:

• OK - There are no opens in the wiring. Proceed to Test Step 8.

• Not OK - There is an open circuit or excessive resistance in the harness or the connectors.

  Repair: Repair the circuit.Verify that the repair eliminates the problem.

  Stop.

Test Step 8. Check for Shorts in the Wiring

1. Turn the keyswitch to the OFF/RESET position.

2. Disconnect the J1/P1 ECM connector and the J34/P34 coolant level sensor connector.

3. Measure the resistance between the following terminals:
   • P1:35 (Digital Sensor +8V) to P1:24 (Coolant Level Sensor)

   • P1:24 (Coolant Level Sensor) to P1:30 (Analog Sensor Return)

   • P1:30 (Analog Sensor Return) to P1:35 (Digital Sensor +8V)

Expected Result:

The resistance should be greater than 20,000 Ohms for each measurement.

Results:

• OK - There are no short circuits in the harness. Proceed to Test Step 9.

• Not OK - There is a short circuit in the harness.

  Repair: Repair the circuit.Verify that the repair eliminates the problem.

  Stop.

Test Step 9. Short the Signal at the ECM

1. Disconnect the J34/P34 coolant level sensor connector.

2. Install a 7X-1715 Adapter Cable (40 Pin Breakout T) at the J1/P1 ECM connector.

3. Turn the keyswitch to the ON position and monitor the status of "Coolant Level" on Cat ET.

4. Install a jumper wire between P1:24 (Coolant Level Sensor) and P1:30 (Analog Sensor Return) at the breakout.

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

Expected Result:

The status should change from "Low" without the jumper wire to "OK" when the jumper wire is installed.

Results:

• OK - The ECM is properly reading the switch input.

  Repair: Refer to Troubleshooting, "Electrical Connectors - Inspect" if the problem is intermittent.

  Stop.

• Not OK - The ECM is not reading the switch input.

  Repair: Verify your results.Temporarily replace the ECM. If the new ECM fixes the problem, permanently install the new ECM.

  Stop.