C7 and C9 Industrial Engines Troubleshooting – Coolant Level – Test

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

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

When the sensor is immersed in coolant, an internal switch is closed. When the internal switch closes, the signal for the engine coolant level is grounded through the sensor return. The Electronic Control Module (ECM) detects the ground on the input for the engine coolant level. If the signal is not present, an event code is generated.

Verify that the coolant level has been programmed to “Enabled” on the configuration screen on the Cat® Electronic Technician (ET). If the coolant level is not programmed, Cat ET will display “Unavailable” for the parameter.

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Schematic of the engine coolant level sensor

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Engine components for the engine coolant level sensor

(1) P61 customer connector

(2) J1/P1 connectors

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Rear view of a typical radiator with an engine coolant level sensor

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P1 terminals that are associated with the engine coolant level sensor

(P1-5) Return

(P1-4) +8 VDC (digital sensor supply)

(P1-49) Engine coolant level

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J61 and P61 terminals that are associated with the engine coolant level sensor

(8) +8 VDC (digital sensor supply)

(15) Return

(36) Engine coolant level

Table 1
Troubleshooting Test Steps	Values	Results
1. Check the Coolant Level A. Stop the engine. Allow the engine to cool. B. Check the coolant level. Refer to the engine Operation and Maintenance Manual for the proper procedure.	Coolant	Results: The coolant level is low. Repair: Add coolant according to the procedure in the Operation and Maintenance Manual. Identify the source of the coolant leak and fix the problem. Verify that the original problem is resolved. Air may be trapped in the cooling system. Purge any air that is trapped in the cooling system. STOP Results: The coolant is at the proper level. Proceed to Test Step 2.
2. Inspect the Electrical Connectors and the Wiring A. Turn the keyswitch to the OFF position. B. Thoroughly inspect connectors (1) and (2). Inspect the J800/P800 connectors for the engine coolant level sensor. Refer to Troubleshooting, “Electrical Connectors – Inspect”. C. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector, the customer connector, and the sensor connector that is associated with the circuit for the engine 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. E. Check the allen head screw on the customer connector for the proper torque. Refer to Troubleshooting, “Electrical Connectors – Inspect” for the correct torque values.	Electrical Connectors and Wiring	Results: The connectors and wiring are OK. Proceed to Test Step 3. Results: There is a problem with the connectors and/or the wiring. Repair: Repair the wiring and/or the connectors. Replace parts, if necessary. Ensure that all of the seals are properly connected. Verify that the original problem is resolved. STOP
3. Short the Harness and Monitor the Status of the “Coolant Level” A. Connect Cat ET to the service tool connector. B. Disconnect the J800/P800 connectors for the engine coolant level sensor. C. Install a jumper wire between P800-B (Digital Sensor Return) and P800-C (Coolant Level Sensor). D. Turn the keyswitch to the ON position. E. Monitor the status of “Coolant Level” on Cat ET while the jumper wire is installed. F. Turn the keyswitch to the OFF position. G. Remove the jumper wire. H. Connect the J800/P800 connectors.	Coolant Level	Results: The status of the “Coolant Level” is “OK” when the jumper wire is installed. The ECM, the signal wire, and the return wire are OK. Proceed to Test Step 4. Results: The status of the “Coolant Level” is not “OK” when the jumper wire is installed. Proceed to Test Step 5.
4. Check the Supply Voltage at the Sensor Connector A. Disconnect the J800/P800 connectors. B. Turn the keyswitch to the ON position. C. Measure the voltage between terminals P800-A (+8 VDC digital sensor supply) and P800-B (Return) at the harness connector for the engine coolant level sensor. D. Turn the keyswitch to the OFF position.	8.0 ± 0.4 VDC	Results: The supply voltage is reaching the sensor. Repair: Replace the engine coolant level sensor. Verify that the original problem is resolved. STOP Results: The supply voltage is not reaching the sensor. Repair: Refer to Troubleshooting, “Sensor Supply – Test”, for the appropriate troubleshooting procedure. STOP
5. Create a Short Circuit at the ECM P1 Connector A. Remove terminals P1-3 and P1-49. Install a jumper wire into open terminals P1-3 and P1-49. B. Turn the keyswitch to the ON position and monitor the status of “Coolant Level” on Cat ET while the jumper wire is installed. C. Remove the jumper wire. Monitor the status of “Coolant Level” on Cat ET. D. Turn the keyswitch to the OFF position.	Short Circuit	Results: The status of the switch is “OK” when the jumper wire is connected. The status of the switch is “Low” when the jumper wire is not connected. The ECM is properly reading the switch input. However, the ECM did not detect the jumper wire at the sensor connector. There is a problem with the wiring. There may be a problem with a connector. Repair: Repair the wiring and/or the connector. Replace parts, if necessary. Verify that the original problem is resolved. STOP Results: The ECM is not reading the switch input. Repair: Replace the ECM. Refer to Troubleshooting, “ECM – Replace”. Verify that the original problem is resolved. STOP

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