C18 Engines for Caterpillar Built Machines Caterpillar

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

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

Illustration 1	g01132350
Coolant level sensor (1) Sensor (2) Brass rod (3) Plastic cover

Coolant level sensor (1) contains no moving parts. The sensor detects variations in capacitance. The sensor's probe contains a brass rod (2) that is covered with plastic (3). The brass rod is one plate of a capacitor. The coolant is the other plate of the capacitor. The plastic cover is the dielectric between the plates of the capacitor.

When the probe is immersed in coolant, the sensor senses a particular capacitance. The sensor responds by creating a short circuit between the signal wire and the ground wire.

When the probe is not immersed in coolant, the capacitance value changes. The change in the capacitance value is detected by the sensor's electronic circuits. The Electronic Control Module (ECM) detects the voltage and the ECM activates one of the following event codes:

• E057 Low Engine Coolant Level Derate

• E058 Low Engine Coolant Level Shutdown

• E059 Low Engine Coolant Level Warning

An event code is probably caused by a low coolant level. The next likely cause is a problem with a wiring harness or with the sensor. The least likely cause is a problem with the ECM.

Illustration 2	g01288782
Schematic for the coolant level sensor

Illustration 3	g01288698
P1 terminal that is associated with the coolant level sensor (P1-47) Coolant level

Illustration 4	g01094844
Sensor connector

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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.

Test Step 1. Inspect the Electrical Connectors and the Wiring

1. Remove the electrical power from the ECM.

2. Thoroughly inspect ECM connector J1/P1. Inspect the connectors for the coolant level sensor. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".

3. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the coolant level sensor.

4. Check the allen head screw on each ECM connector for the proper torque. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".

Expected Result:

All connectors, pins, and sockets are completely coupled and/or inserted, and the harness and wiring are free of corrosion, of abrasion and of pinch points.

Results:

• OK - The connectors and wiring are OK. Proceed to Test Step 2.

• Not OK - There is a problem with the connectors and/or the wiring.

  Repair: Repair the wiring and connectors or replace the wiring or the connectors. Ensure that all of the seals are properly connected. Verify that the repair eliminates the problem.Verify that the repair eliminates the problem.

  STOP

Test Step 2. Check the Supply Voltage at the Sensor Connector

1. Disconnect the coolant level sensor.

2. Restore the electrical power to the ECM.

3. Measure the voltage between terminals A (+24 VDC) and B (Return) at the harness connector for the coolant level sensor.

4. Remove the electrical power from the ECM.

Expected Result:

The voltage measurement is 24.0 ± 2.0 VDC.

Results:

• OK - The voltage measurement is 24.0 ± 2.0 VDC. The supply voltage is reaching the sensor. Proceed to Test Step 3.

Test Step 3. 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 the electrical power from the ECM.

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

Expected Result:

The coolant is at the proper level.

Results:

• OK - The coolant is at the proper level. Proceed to Test Step 4.

• 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 4. Disconnect the Coolant Level Sensor and Monitor the Status of "Coolant Level"

1. Connect the Caterpillar Electronic Technician (ET) to the service tool connector. Refer to electronic troubleshooting Troubleshooting, "Electronic Service Tools".

2. Disconnect the connector for the coolant level sensor.

3. Restore the electrical power to the ECM.

4. Monitor the status of "Coolant Level" on Cat ET.

5. Remove the electrical power from the ECM.

Expected Result:

The status changes from "OK" to "Low" when the sensor is disconnected.

Results:

• OK - The status is "Low" when the sensor is disconnected. Proceed to Test Step 5.

• Not OK - The status is "OK" when the sensor is disconnected. Proceed to Test Step 6.

Test Step 5. Short the Harness and Monitor the Status of "Coolant Level"

1. Restore the electrical power to the ECM and monitor the status of "Coolant Level" on Cat ET.

2. Install a jumper wire between terminals B (Return) and C (Signal) on the harness connector for the coolant level sensor.

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

4. Remove the jumper wire.

5. Remove the electrical power from the ECM.

Expected Result:

The status changes from "Low" to "OK" when the jumper wire is installed.

Results:

• OK - The status changes from "Low" to "OK" when the jumper wire is installed. The ECM and the wiring to the coolant level sensor are OK. There may be a problem with the coolant level sensor.

  Repair: Perform the following procedure:

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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. Drain the coolant below the level of the coolant level sensor.

  2. Restore the electrical power to the ECM and monitor the status of "Coolant Level" on Cat ET.

  3. Remove the electrical power from the ECM.

     If the status of the "Coolant Level" is "OK", replace the sensor. Verify that the problem is resolved.

     If the status for the coolant level is "Low", fill the cooling system according to the procedure in the Operation and Maintenance Manual. Return the engine to service.

  STOP

• Not OK - Shorting the harness does not affect the status on Cat ET. Proceed to Test Step 6.

Test Step 6. Check the Wiring for an Open Circuit

1. Remove the electrical power from the ECM.

2. Disconnect the J1/P1 and J2/P2 connectors.

3. Disconnect the return wire from engine ground.

4. Disconnect the wire for +24.0 ± 2.0 VDC from +Batt.

Note: Wiggle the harness during the following measurements in order to reveal an intermittent condition.

5. Measure the resistance of the following wires:
   • The wire for +24.0 ± 2.0 VDC from +Batt to A (+24 VDC) on the sensor connector

   • Return wire from engine ground to B (Return) on the sensor connector

   • P1-47 (Engine Coolant Level) to C (Engine Coolant Level) on the sensor connector

Expected Result:

Each resistance measurement is less than ten Ohms.

Results:

• OK - Each resistance measurement is less than ten Ohms. There are no opens in the wiring. Proceed to Test Step 7.

• Not OK - At least one resistance measurement is greater than ten Ohms. There is an open circuit or excessive resistance in the harness. There may be a problem in a connector.

  Repair: Repair the wire and/or the connector, when possible. Replace parts, if necessary. Verify that the problem is resolved.

  STOP

Test Step 7. Check the Wiring for a Short Circuit

1. Remove the electrical power from the ECM.

Note: Wiggle the harness during the following measurements in order to reveal an intermittent condition.

2. Measure the resistance between the points that are listed in Table 1. Be sure to wiggle the wires in the harnesses as you make each resistance measurement.
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   Table 1

   Resistance Measurements for the Circuit for the Coolant Level Sensor
   Connector and Terminal	Terminal
   P1-47 (Engine Coolant Level)	All of the other terminals on the P1 connector
   	All of the terminals on the P2 connector
   	Engine ground

Expected Result:

Each check of the resistance indicates an open circuit.

Results:

• OK - Each check of the resistance indicates an open circuit. Proceed to Test Step 8.

• Not OK - At least one check of the resistance does not indicate an open circuit. There is a problem in the harness. There may be a problem in a connector.

  Repair: Repair the wire and/or the connector, when possible. Replace parts, if necessary. Verify that the problem is resolved.

  STOP

Test Step 8. Create a Short Circuit at the ECM

1. Remove the terminal from location P1-47.

2. Install the ends of a jumper wire into locations P1-47 and engine ground. This will create a short circuit at the ECM connectors.

3. Restore the electrical power to the ECM and monitor the status of "Coolant Level" on Cat ET.

4. Remove the jumper wire. Monitor the status of "Coolant Level" on Cat ET.

Expected Result:

The status is "Low" when the jumper wire is not connected. The status is "OK" when the jumper wire is connected.

Results:

• OK - The status is "Low" when the jumper wire is not connected. The status is "OK" when the jumper wire is connected. The ECM is properly reading the switch input.

  Repair: Perform the following procedure:

  1. Remove the jumper wire from the ECM connectors.

  2. Install the terminal into the correct locations on the ECM connectors. Pull on the wire in order to verify proper installation of the terminal.

     The problem appears to be resolved. The original problem was probably caused by a poor electrical connection. Return the engine to service.

  STOP

• Not OK - The status is "Low" when the jumper wire is connected. The ECM is not reading the switch input.

  Repair: Temporarily install a new ECM. Refer to electronic troubleshootingTroubleshooting, "Replacing the ECM".If the new ECM works correctly, install the original ECM and verify that the problem returns. If the new ECM works correctly and the original ECM does not work correctly, replace the original ECM. Verify that the problem is resolved.

  STOP