C27 and C32 Industrial and Petroleum Engines Caterpillar

Use this procedure to troubleshoot the 111-02 Engine Coolant Level Loss of Signal.

The coolant level sensor monitors the engine coolant level in order to warn the operator in the event that the coolant level is low. The coolant level sensor is located on the side of the expansion tank or radiator.

Illustration 1	g01150024
Coolant level sensor (1) Sensor (2) Sensor probe (brass dowel) (3) Plastic cover

Coolant level sensor (1) contains no moving parts. The sensor provides the same function as a switch. The state of the switch is dependent on the capacitance value that is detected. The sensor contains a probe (2) that is covered with plastic (3) .

When the probe is immersed in coolant, the sensor senses a particular capacitance. The sensor's electronics react by sinking the signal to the digital return (ground).

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 sensor sources approximately +5 VDC to the signal wire. The Electronic Control Module (ECM) detects the voltage and the ECM activates an event code.

Note: This feature is optional and the system configuration parameter for "Coolant Level Sensor" must be configured to "Installed". If the ECM parameter is not programmed, the engine monitoring system will not monitor the status of the sensor. Refer to Troubleshooting, "System Configuration Parameters".

The event code for low coolant level is used to indicate that an abnormal condition exists for the engine. A low coolant level may cause damage to the engine. Correct this condition immediately.

The most likely cause of an active diagnostic code that is related to the coolant level sensor is a loose connection in a connector. The next likely cause is a problem with the coolant level sensor or a problem with a wiring harness. The least likely cause is a problem with the ECM.

Illustration 2	g01167362
Typical location of the coolant level sensor (4) Coolant level sensor

Illustration 3	g03428338
Schematic for coolant level sensor

Test Step 1. Inspect the Electrical Connectors and the Wiring

1. Turn the keyswitch to the OFF position.

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Illustration 4	g01167370
Engine view (5) J1/P1 ECM connectors

2. Thoroughly inspect connectors (5) . Also, thoroughly inspect the connectors for sensor (4) . Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

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Illustration 5	g03428341
P1 ECM connector (P1-4) +8 V digital supply (P1-5) Sensor return (P1-49) Coolant level sensor

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Illustration 6	g01159881
Harness connector for the coolant level sensor (A) +8 V digital supply (B) Sensor return (C) Coolant level sensor

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 Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.

Expected Result:

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

2. Turn the keyswitch to the ON position.

3. Measure the voltage between terminals A (+8 V digital supply) and B (sensor return) at the harness connector for the coolant level sensor.

4. Turn the keyswitch to the OFF position.

Expected Result:

The voltage measurement is 8.0 ± 0.4 VDC.

Results:

• OK - The voltage measurement is 8.0 ± 0.4 VDC. The supply voltage is reaching the sensor. Proceed to Test Step 3.

• Not OK - The voltage measurement is not 8.0 ± 0.4 VDC. The digital sensor supply voltage is not reaching the sensor.

  Repair: Refer to Troubleshooting, "Digital Sensor Supply Circuit - Test".

  STOP

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. 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 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 Troubleshooting, "Electronic Service Tools".

2. Disconnect the J800/P800 connectors.

3. Turn the keyswitch to the ON position.

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

5. Turn the keyswitch to the OFF position.

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

2. Install a jumper wire between terminals B (sensor return) and C (coolant level sensorl) 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. Turn the keyswitch to the OFF position.

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.

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

  3. Turn the keyswitch to the OFF position.

     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", connect the sensor. 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 for Opens in the Wiring

1. Turn the keyswitch to the OFF position.

2. Disconnect the J2/P2 ECM connector and the J800/P800 coolant level sensor connector.

3. Measure the resistance between the following terminals:
   • P1-4 (+8 V digital supply) to P800-A (+8 V digital supply)

   • P1-5 (sensor return) to P800-B (sensor return)

   • P1-49 (coolant level sensor) to P800-C (coolant level sensor)

Expected Result:

The resistance is less than five Ohms for each measurement.

Results:

• OK - The resistance is less than five Ohms for each measurement. There are no opens in the wiring. Proceed to Test Step 7.

• Not OK - The resistance is greater than five Ohms for each measurement. 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 7. Check the Wiring for a Short Circuit

1. Turn the keyswitch to the OFF position.

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
   P1-49 (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 P1-5 sensor return and P1-49 coolant level signal.

2. Install the ends of a jumper wire into locations P1-5 and P1-49. This will create a short circuit at the ECM connectors.

3. Turn the keyswitch to the ON position 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 connector.

  2. Install the two terminals into the correct locations on the ECM connector. Perform a pull test on the two wires in order to verify proper installation of the terminals.

     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 Troubleshooting, "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