FILM 7C4085 - Caterpillar

System Operation Description:Use this procedure to troubleshoot diagnostic codes for open circuits or short circuits for the engine coolant temperature sensor.This procedure covers the following diagnostic codes:
110-3 Engine Coolant Temperature Sensor : Voltage Above Normal
110-4 Engine Coolant Temperature Sensor : Voltage Below NormalThe engine coolant temperature sensor does not require +5 VDC from the Electronic Control Module (ECM). The engine coolant temperature sensor is a passive sensor of the analog type. The sensor operates without a voltage supply from the ECM.A -3 code is probably caused by a problem in an engine harness. There may be an open circuit in a harness, or a short circuit to a positive voltage source in a harness. The next likely cause is a sensor problem. The least likely cause is a problem with the ECM.An -4 code is probably caused by a short circuit to ground in an engine harness. The next likely cause is a sensor problem. The least likely cause is a problem with the ECM.Logged diagnostic codes provide a historical record. Before you begin this procedure, use Caterpillar Electronic Technician (ET) to print the logged codes to a file.This troubleshooting procedure may generate additional diagnostic codes. Keep your mind on correcting the cause of the original diagnostic code. Clear the diagnostic code after the problem is resolved.
Illustration 1 g01325355
Schematic for the analog sensor
Test Step 1. Inspect the Electrical Connectors and Wiring
Remove the electrical power from the engine. Note: For the following steps, refer to Troubleshooting, "Electrical Connectors - Inspect".
Thoroughly inspect each of the following connectors:
J1/P1 connectors
J7/P7 connectors
Check the torque of the allen head screws for the ECM connectors.
Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the analog sensors.
Check the harness and wiring for abrasion and for pinch points from the analog sensors to the ECM. Expected Result:All connectors, pins, and sockets are connected properly. The connectors and the wiring do not have corrosion, abrasion, or pinch points.Results:
OK - All connectors, pins, and sockets are connected properly. The connectors and the wiring do not have corrosion, abrasion, or pinch points. The components are in good condition with proper connections. If you are troubleshooting a -3 code, proceed to Test Step 3. If you are troubleshooting a -4 code, proceed to Test Step 2.
Not OK - At least one of the connectors, pins, and/or sockets are not connected properly. At least one of the connectors and/or the wiring has corrosion, abrasion, or pinch points.Repair: Perform the necessary repairs and/or replace parts, if necessary.STOPTest Step 2. Create an Open Circuit for the Sensor
Disconnect the sensor that has the "voltage below normal" diagnostic code.
Observe the "Active Diagnostic" screen on Cat ET. Allow a minimum of 30 seconds for any codes to activate. Look for an active -3 diagnostic code. Expected Result:There is an active -3 diagnostic code for the disconnected sensor.Results:
Yes - Before the suspect