EDGE-CUTTING 1359576 - Caterpillar

Illustration 1 g00850906
Simplified System Schematic For Engine Coolant Loss SensorThe sensor is powered by an 8 volt sensor supply from the GSC. When coolant is NOT present at the sensor, a high signal is sent to the GSC. A high signal is approximately +5 DCV. When coolant is present at the sensor, a low signal (battery negative) is sent to the GSC.Note: The GSC is usually programmed to treat coolant loss sensor problems as an alarm fault. P04 is equal to 0. If the GSC is programmed to shutdown, P04 is equal to 1. The operator is not required to press the "Alarm Codes" key in order to view the CID 111 FMI 3. The CID 111 FMI 3 is automatically shown on the upper display.The possible causes of a CID 111 FMI 3 are listed below.
A short to +battery of the sensor signal
An open circuit of the sensor signalBegin performing these procedures only when CID 111 FMI 3 is showing and the "DIAG" indicator is FLASHING on the upper display. The flashing indicator means that the diagnostic code is active. The GSC treats a CID 111 FMI 3 as an alarm fault. Active alarm faults are shown on the display when the key is pressed and the engine control switch (ECS) is in any position except the OFF/RESET position. For an inactive fault, the problem may be intermittent. See Testing And Adjusting, "Electrical Connector - Inspect" in order to troubleshoot an inactive fault. Also use the preceding system schematic. Clear the fault from the fault log after troubleshooting is complete.Note: If a CID 269 FMI 3 or a CID 269 FMI 4 is active, correct the diagnostic code prior to proceeding with this procedure.Test Step 1. CHECK THE SENSOR VOLTAGE SUPPLY CIRCUIT.
Turn the ECS to OFF/RESET. Then, turn the ECS to the STOP position.
Disconnect the sensor from the engine harness. The sensor remains fastened to the engine.
At the engine harness side of the sensor connector, measure the voltage (DCV) that is between contact "A" and contact "B". Contact "A" is the supply for the sensor. Contact "B" is the sensor ground.Expected Result:The voltage should be 8.0 DCV ( 0.5 DCV).Results:
- The voltage is 8.0 DCV ( 0.5 DCV). Proceed to Test Step 2.
NOT OK - The sensor voltage supply circuit has failed. Proceed to Test Step 5.Test Step 2. CHECK THE SIGNAL CIRCUIT.
Turn the ECS to OFF/RESET. Then, turn the ECS to the STOP position.
Disconnect the sensor from the engine harness. The sensor remains fastened to the engine.
At the engine harness side of the sensor connector, measure the voltage (DCV) between contact "C" and contact "B". Contact "C" is the signal. Contact "B" is the sensor ground.Expected Result:The voltage should be 2.5 DCV ( 0.5 DCV).Results:
The voltage is 2.5 DCV ( 0.5 DCV) - The signal circuit functions properly. Proceed to Test Step 3.
The voltage is equal to battery positive - The engine harness has failed. Repair: The signal circuit that is within the engine harness is shorted