3512C and 3516C Marine Auxiliary Engines Caterpillar

Coolant Level - Test

Usage:

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.

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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 signal wire. When this condition is detected by the Electronic Control Module (ECM), an event 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 sensor configuration parameter must be set to "Installed" in order for the ECM to monitor the signal from the sensor.

The activation of an event 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.

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Illustration 2	g02949436

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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

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Table 1
Troubleshooting Test Steps	Values	Results
1. Inspect the Electrical Connectors and the Wiring A. Turn the main disconnect switch to the OFF position. B. Thoroughly inspect the ECM connectors and all other connectors connected with the sensors. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details. C. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the coolant level sensor. D. Check the allen head screw on each ECM connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.	Electrical Connectors and the Wiring	Result: The harnesses and the wiring appear to be OK. Proceed to Test Step 2. Result: There is a problem with the connectors and/or the wiring. 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.
2. Check the Supply Voltage at the Sensor Connector A. Disconnect the coolant level sensor at the sensor connector. B. Restore electrical power to the ECM. C. Measure the voltage between terminals A (supply) and B (return) at the harness connector for the coolant level sensor. D. Turn the main disconnect switch to the OFF position.	8.0 ± 0.2 VDC	Result: The voltage measurement is 5.0 ± 0.4 VDC. The supply voltage is reaching the sensor. Proceed to Test Step 3. Result: The voltage measurement is not 5.0 ± 0.4 VDC. The sensor supply voltage is not reaching the sensor. There is a problem in the circuit for the digital sensor supply. Refer to Troubleshooting, "Sensor Supply - Test".
3. Disconnect the Coolant Level Sensor and Monitor the Status for "Coolant Level" A. Disconnect the harness connector for the coolant level sensor. B. Restore electrical power to the ECM. C. Monitor the status of "Coolant Level" on Cat ET. Wait at least 30 seconds for activation of the status indicator.	Sensor reading	Result: The status is "LOW" when the sensor is disconnected. There may be a problem with the coolant level sensor. Proceed to Test Step 4. Result: The status is "OK" when the sensor is disconnected. The problem is between the ECM and the harness connector. There may be a problem with the ECM. Proceed to Test Step 5.
4. Short the Signal Wire to Ground and Monitor the Status for "Coolant Level" A. Turn the main disconnect switch to the OFF position. B. Fabricate a jumper wire that is long enough to create a short circuit between two terminals at the coolant level sensor harness connector. Crimp connector pins to each end of the jumper wire. C. Install the jumper wire between terminals B (return) and C (sensor signal) on the harness side of the connector for the coolant level sensor. D. Restore electrical power to the ECM. E. Monitor the status of "Coolant Level" on Cat ET while the jumper wire is installed. Wait at least 30 seconds for activation of the status indicator. F. Turn the main disconnect switch to the OFF position. G. Remove the jumper wire. Connect the harness connector for the coolant level sensor.	Short circuit	Result: 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 Perform the following procedure: 1. Drain the coolant below the level of the coolant level sensor. 2. Restore electrical power to the ECM. 3. Monitor the status of "Coolant Level" on Cat ET. Wait at least 30 seconds for activation of the status indicator. 4. Turn the main disconnect switch to the OFF position. If the status of the "Coolant Level" is "OK", replace the sensor. If the status for the coolant level is "LOW", the circuit for the coolant level sensor is OK. There may be an intermittent problem in the harness or in a connector. Fill the cooling system according to the procedure in the Operation and Maintenance Manual. Return the engine to service. If an intermittent electrical problem is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect" for troubleshooting information. Result: Shorting the harness does not affect the status on Cat ET. The problem is between the ECM and the harness connector. There may be a problem with the ECM. Proceed to Test Step 5.
5. Check the Wiring Harness for an Open Circuit A.Turn the main disconnect switch to the OFF position. B. Disconnect the J1/P1 ECM connector and the connector for the coolant level sensor. C. Fabricate a jumper wire that is long enough to provide a test circuit between the ECM connector and the sensor connector. Crimp a connector pin to one end of the jumper wire. D. Install the jumper wire connector pin into terminal C on the harness side of the connector for the appropriate sensor. E. Measure the resistance between terminal P1-44 engine coolant level and the loose end of the jumper wire. Or, measure the resistance between terminal P2-74 SCAC coolant level and the loose end of the jumper wire. The correct resistance measurement is a short circuit. Remove the jumper wire. Leave the sensor connector disconnected.	Open circuit	Result: The measurement indicated a short circuit. There is not an open circuit in the harness wire for the sensor signal. Proceed to Test Step 6. Result: The measurement did not indicate a short circuit. There is an open circuit or excessive resistance in the harness or the connectors. Repair the wire and/or the connector, when possible. Replace damaged parts, if necessary. Verify that the repair eliminates the problem.

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Table 2
Resistance Measurements for the Coolant Level Circuit
Connector and Terminal	Terminal
P1-44 (engine coolant level) P2-74 (SCAC coolant level)	All of the terminals on the P1 connector
	All of the other terminals on the P2 connector
	Engine ground stud

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Table 3
Troubleshooting Test Steps	Values	Results
6. Check the Harness Wiring for a Short Circuit A. Turn the main disconnect switch to the OFF position. B. Disconnect the J1/P1 and the J2/P2 ECM connectors. Also, disconnect the connector for the coolant level sensor. C. Measure the resistance between the points that are listed in Table 2. Wiggle the harness during the following measurements in order to reveal an intermittent condition.	Short circuit	Result: Each check of the resistance indicates an open circuit. There is not a short circuit to another wire in the harness. Proceed to Test Step 7. At least one check of the resistance does not indicate an open circuit. There is a short to another wire in the harness. The problem may be with a connector. Repair the wire and/or the connector, when possible. Replace damaged parts, if necessary. Verify that the repair eliminates the problem.
7. Check the Operation of the ECM A. Fabricate a jumper wire that is long enough to provide a test circuit across the ECM connectors. Crimp connector sockets to each end of the jumper wire. B. Remove the wires from terminal locations P2-30 (secondary ECM return) and P1-44 (primary ECM coolant level). Install the jumper wire into these terminal locations. Or, remove the wires from terminal locations P2-30 (secondary ECM return) and P2-74 (primary ECM SCAC coolant level). Install the jumper wire into these terminal locations. C. Restore electrical power to the ECM. D. Use Cat ET to monitor the status for "Coolant Level". Use a wire removal tool to remove the jumper wire and check the status again. Wait at least 30 seconds for activation of the status indicator. E. Turn the main disconnect switch to the OFF position. Restore all wiring to the original configuration.	Operation of ECM	Result: 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. There may be an intermittent problem in the harness or in a connector. If an intermittent electrical problem is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect" for troubleshooting information. Result:The status is "LOW" when the jumper wire is connected. RepairReplace the ECM. Refer to Troubleshooting, "Test ECM Mode". Note: Before you consider replacing the ECM, consult with the Dealer Solutions Network (DSN) for assistance. Verify that the repair eliminates the problem.

If the procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).