Coolant Level - Test
Use this procedure to troubleshoot any suspect problems with the circuits for the coolant level sensors.
The coolant level sensors monitor the engine coolant level to warn the operator when the coolant level is low. The coolant level sensors are located on the expansion tank.
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| Illustration 1 | g01150024 |
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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 depends on the capacitance value that is detected at the probe of the sensor. The sensor contains a probe (2) that is covered with plastic (3).
When the sensors probe is immersed in coolant, the sensor senses a particular capacitance. The sensors electronics react by sinking the signal to the digital return (ground).
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 Cat 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 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. The least likely cause is a problem with the ECM.
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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. |
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| Troubleshooting Test Steps | Values | Results |
|---|---|---|
1. Check the Coolant Level A. Remove electrical power from the ECM. Note: Allow the engine to cool prior to removal of the cooling system pressure cap. B. Check the coolant level. Refer to the Operation and Maintenance Manual for the proper procedure to check the coolant level. |
Coolant Level |
Result: The coolant is at the proper level. Proceed to Test Step 2. Result: The coolant level is low. 1. Add coolant according to the procedure in the Operation and Maintenance Manual. 2. There may be a leak in the cooling system. 3. Identify the source of the coolant leak. 4. Repair the leak. |
2. Verify that the Parameter for the appropriate “Coolant Level Sensor” is Programmed Correctly A. Remove electrical power from the ECM. B. Connect the Cat ET to the service tool connector. C. Restore electrical power to the ECM. D. Establish communication with the ECM. E. Verify that the parameter for the suspect “Coolant Level Sensor” is programmed to “Installed”. |
Coolant Level Sensor |
Result: The “Coolant Level Sensor” parameter is programmed correctly. Proceed to Test Step 3. Result: The “Coolant Level Sensor” parameter is not programmed correctly. Program the “Coolant Level Sensor” parameter to "Installed". Verify that the repair eliminates the problem. |
3. Inspect the Electrical Connectors and the Wiring A. Remove electrical power from the ECM. B. Thoroughly inspect the connectors for sensor (4). Also, thoroughly inspect ECM connectors (5). Refer to Troubleshooting, "Electrical Connectors - Inspect" for details. C. Perform a 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 |
Result: The harnesses and the wiring appear to be OK. Proceed to Test Step 4. 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. |
4. Check the Supply Voltage at the Sensor Connector A. Disconnect the suspect coolant level sensor at the sensor connector. B. Restore electrical power to the ECM. C. Measure the voltage between terminals A (digital sensor supply) and B (digital return) at the harness connector for the coolant level sensor. D. Remove electrical power from the ECM. |
8.0 ± 0.4 VDC |
Result: The voltage measurement is 8.0 ± 0.4 VDC. The supply voltage is reaching the sensor. Proceed to Test Step 5 Result: The digital 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". STOP |
5. Disconnect the Suspect Coolant Level Sensor and Monitor the Status for the Sensor A. Disconnect the harness connector for the suspect coolant level sensor. B. Restore electrical power to the ECM. C. Monitor the status of the appropriate “Coolant Level” on Cat ET. Note: Wait at least 30 seconds for activation of the status indicator. D . Remove electrical power from the ECM. |
Coolant Level Sensor |
Result: The status is “LOW” when the sensor is disconnected. There may be a problem with the coolant level sensor. Proceed to Test Step 6. Result: The status is “OK” when the sensor is disconnected. The problem is between the ECM and the harness connector. Proceed to Test Step 7. |
6. Short the Signal Wire to Ground and Monitor the Status for the appropriate “Coolant Level” A. Remove electrical power from the ECM. B. 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. C . Install the jumper wire between terminals B (digital 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 the appropriate "Coolant Level" on Cat ET while the jumper wire is installed. Note: Wait at least 30 seconds for activation of the status indicator. F. Remove electrical power from the ECM. G. Remove the jumper wire. Connect the harness connector for the coolant level sensor. |
The status changes from “LOW” to “OK” when the jumper wire is installed. |
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. Result: The ECM and the wiring harness to the coolant level sensor are NOT OK. 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 the appropriate “Coolant Level” on Cat ET. Note: Wait at least 30 seconds for activation of the status indicator. 4. Remove electrical power from the ECM. 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. STOP NOT OK - 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 7. |
7. Check the Wiring Harness for an Open Circuit Note: This is a continuity test for the signal wire of the sensor circuit in question. This action will be done by measuring the resistance of the suspected wire. You will fabricate a jumper wire that will essentially extend the meter lead of the measuring device. A. Remove electrical power from the ECM. B. Disconnect the J2/P2 ECM connector and the connector for the appropriate 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 wires connector pin into terminal C on the harness side of the connector for the appropriate coolant level sensor. E. Measure the resistance between the loose end of the jumper wire and the appropriate P2 connector terminal for the wire under test. Remove the jumper wire. Leave the sensor connector disconnected. |
The measurement indicates a short 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 8. 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. STOP |
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| Resistance Measurements for the Coolant Level Circuit | |
|---|---|
| Connector and Terminal | Terminal |
| P1-45 (Engine Coolant level) | All the terminals on the P1 connector |
| Engine ground stud | |
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| Troubleshooting Test Steps | Values | Results |
|---|---|---|
8. Check the Harness Wiring for a Short Circuit A. Remove electrical power from the ECM. B. Disconnect the J1/P1 and the J2/P2 ECM connectors. Also, disconnect the connector for the suspect coolant level sensor. C. Measure the resistance between the terminal of the appropriate sensor in the first column of Table 3. Note: Wiggle the harness during the measurements to reveal an intermittent condition. |
Each check of the resistance indicates an open 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 9. Result: 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 problem is resolved. STOP |
9. Check the Operation of the ECM Note: The ECM will be tested by opening and shorting the sensor signal input to the digital return input at the J1 ECM connector. This test covers the coolant level sensors for the engine coolant. A. Use a wire removal tool to remove the appropriate sensor signal wire and digital return wire from the P2 connector. B. Fabricate a jumper wire that is long enough to provide a test short circuit across the ECM connector. Crimp connector sockets to each end of the jumper wire. C. Install the jumper wire into the empty terminal locations. D. Restore electrical power to the ECM. E. Use Cat ET to monitor the status for the appropriate “Coolant Level”. Use a wire removal tool to remove the jumper wire and check the status again. F. Remove electrical power from the ECM. Restore all wiring to the original configuration. |
The status is “LOW” when the jumper wire is not connected. The status is “OK” when the jumper wire is connected. |
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. STOP Result: The status is “LOW”when the jumper wire is connected. The ECM is not reading the switch input. Replace the ECM. Refer to Troubleshooting, "ECM - Replace". STOP |
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