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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 sensor 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.
Illustration 2 g02944238
Table 1
Troubleshooting Test Steps Values Results
1. Check the Coolant Level
Allow the engine to cool prior to removal of the cooling system pressure cap.
A. Remove electrical power from the ECM.
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.
Add coolant according to the procedure in the Operation and Maintenance Manual.
There may be a leak in the cooling system. Identify the source of the coolant leak. Repair the leak. Refer to Systems Operation/Testing and Adjusting, "Cooling System" for additional information.
2. Verify that the "Coolant Level Sensor" Parameter is Programmed Correctly
A. Connect Cat ET to the service tool connector.
B. Establish communication with the ECM.
C. Verify that the "Coolant Level Sensor" parameter is programmed to "Installed".
D. Remove electrical power from the ECM.
Parameter programmed
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.
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
Table 2
Troubleshooting Test Steps Values Results
3. 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 (sensor supply) and B (sensor return) at the harness connector for the coolant level sensor.
D. Remove electrical power from the ECM.
8.0 0.5 VDC
Result: The voltage measurement is 8.0 0.5 VDC.
The supply voltage is reaching the sensor. Proceed to Test Step 4.
Result: The voltage measurement is not 8.0 0.5 VDC.
The sensor supply voltage is not reaching the sensor. There is a problem in the circuit for the sensor supply. Repair the wiring between the sensor and the ECM.
4. Short the Signal Wire to Ground and Monitor the Status for "Coolant Level"
A. 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.
B. Install the jumper wire between terminals B (sensor return) and C (sensor signal) on the harness side of the connector for the coolant level sensor.
C. Restore electrical power to the ECM.
D. 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.
E. Remove the jumper wire. Connect the harness connector for the coolant level sensor.
The voltage is within 5 VDC of battery voltage
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.
Replace the coolant level sensor. Verify that the repair eliminates the problem.
Result: The status does not change from "LOW" to "OK" when the jumper wire is installed.
The problem is between the ECM and the sensor connector. Repair the wiring. Verify that the repair eliminates the problem.
Complete the procedure in the order in which the steps are listed.