0435896 JOHNSON PISTON, Std.

Illustration 1 g01150024
Coolant level sensor (1) Sensor (2) Sensor probe (brass dowel) (3) Plastic coverCoolant 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.An event code is probably caused by a low coolant level. The next likely cause is a problem with a wiring harness or with the sensor. The least likely cause is a problem with the ECM.Note: If the coolant has been changed recently, ensure that the air has been purged from the cooling system. Refer to Systems Operation/Testing and Adjusting.
Illustration 2 g01150032
Typical location of the coolant level sensor (4) Coolant level sensor
Illustration 3 g01251529
Schematic for coolant level sensor
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.
Test Step 1. Inspect the Electrical Connectors and the Wiring
Remove the electrical power from the ECM.
Illustration 4 g01251539
Typical engine view (5) J1/P1 connectors
Thoroughly inspect connectors (5). Inspect the connectors for sensor (4). Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".
Illustration 5 g01251546
P1 ECM connector (P1-4) +8 V digital supply (P1-5) Digital sensor return (P1-46) Coolant level sensor
Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the coolant level sensor.
Check the allen head screw on each ECM connector for the proper torque. Refer to the diagnostic functional test 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.STOPTest Step 2. Check the Supply Voltage at the Sensor Connector
Disconnect the coolant level sensor.
Restore the electrical power to the ECM.
Illustration 6 g01132478
Harness connector for the coolant level sensor (A) +8 VDC (B) Return
Measure the voltage between terminals A (+8 VDC) and B (return) at the harness connector for the coolant level sensor.
Remove the electrical power from the ECM.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 the diagnostic functional test Troubleshooting, "Digital Sensor Supply Circuit - Test".STOPTest Step 3. Check the Coolant Level
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.
Stop the engine.
After allowing the engine to cool, check the coolant level. Refer to Operation and Maintenance Manual.Note: If the coolant has been changed recently, ensure that the air has been purged from the cooling system. Refer to Systems Operation/Testing and Adjusting.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 to the cooling system.Verify that the repair eliminates the problem. Identify the source of the coolant leak and fix the problem.STOPTest Step 4. Disconnect the Coolant Level Sensor and Monitor the Status of "Coolant Level"
Connect the Caterpillar Electronic Technician (ET) to the service tool connector. Refer to electronic troubleshooting Troubleshooting, "Electronic Service Tools".
Disconnect the sensor connectors.
Restore the electrical power to the ECM.
Monitor the stat