SHAFT-PIVOT 8E2900 - Caterpillar

System Operation Description:The most likely cause of a coolant level alarm is a low coolant level. The next likely cause of a coolant level alarm is a problem in the circuit. The least likely cause of a coolant level alarm is the engine's Electronic Control Module (ECM).Use this procedure in order to troubleshoot any suspect problems with the coolant level sensor(s) or with the wiring circuit. The coolant level sensor 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.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 sensor return (-Battery).When the probe is not immersed in coolant, approximately +5 VDC is sourced to the signal wire. When this condition is detected by the ECM, an alarm for low coolant is generated.
Illustration 1 g01411138
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.
Illustration 2 g01435103
ECM (1) J1/P1 connectors (2) J2/P2 connectors
Thoroughly inspect connectors (1) and (2). Also, thoroughly inspect any connections that are associated with the coolant level circuit. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Illustration 3 g01435093
J1/P1 ECM connector (P1-2) Coolant level (P1-29) Digital sensor return (P1-35) +8 V digital supply
Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the coolant level sensor(s).
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 and 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 electrical power to the ECM.
Illustration 4 g01159881
Terminal locations at the harness connector for the coolant level sensor (Terminal A) Digital sensor supply (Terminal B) Sensor return (Terminal C) Sensor signal
Measure the voltage between terminals A (+8 VDC) and B (return) at the harness connector for the coolant level sensor.
Remove 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