PIPE 5I7548 - Caterpillar

System Operation Description: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 in the event that the coolant level is low. The coolant level sensor is located on the expansion tank.
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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 at the probe of the sensor. The sensor contains a probe (2) that is covered with plastic (3) .When the sensor's 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, 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's 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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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 electrical power from the ECM.
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Location of the coolant level sensor (typical left front engine view) (4) Coolant level sensor
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Location of the ECM connectors (typical engine view) (5) J1/P1 connectors
Thoroughly inspect the connectors for sensor (4). Also, thoroughly inspect ECM connectors (5). Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
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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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Harness connector for the coolant level sensor (A) Sensor supply (B) Sensor return (C) Sensor signal
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 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 harnesses and the wiring appear to be OK. Proceed to Test Step 2.
Not OK - There is a problem with the