GEAR-PUMP DRIVE 1317419 - Caterpillar

Illustration 1 g02025271
Radiator Fan Speed sensor circuit schematicThis diagnostic code is recorded when the ECM receives intermittent signals from the engine cooling fan speed sensor (CID 0544) while the engine is running. An FMI 08 diagnostic code indicates the machine ECM has determined the sensor output signal voltage has an abnormal frequency, pulse width, or period. This Hall-effect type fan speed sensor is mounted near the center of the viscous fan drive clutch. The fan speed sensor is not separately serviceable from the fan drive clutch assembly. The ECM fan speed map uses actual fan speed, coolant temperature, and engine rpm inputs to determine the targeted fan speed. For more information, refer to Special Instruction, REHS4721, "Operation, Troubleshooting and Testing of the Viscous Coupling". Possible causes for this active diagnostic code are:
Sensor output wire is open
Sensor output wire is short to +battery
Sensor output wire is short to ground
Failed sensor
Failed viscous clutch
Failed machine ECM (most unlikely)Note: The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes now, but clear those codes after the original diagnostic code has been corrected. Note: Poor connections are often the cause of a problem in electrical circuits. Before performing this procedure, inspect all of the harness connectors involved in the circuit. Verify that all of the connections in the circuit are clean, secure, and in good condition. If a problem is found with any of the connections: correct the problem and verify that the 544-8 diagnostic code is still active, before performing the following procedures. Note: Check for other related diagnostic codes before performing the following diagnostic code procedure. If a 248-12 diagnostic code for the data link exists, correct the data link problem. Then view the status of the other diagnostic codes and correct the other active codes.System Response:If a fan speed signal is not supplied to the machine ECM, the fan will default to maximum fan speed.Test Step 1. CHECK THE SENSOR OUTPUT FOR AN OPEN CIRCUIT
Turn the key start switch and the disconnect switch to the OFF position. Note: The engine cooling fan speed sensor circuit wires are routed through the viscous fan drive clutch harness connector.
Disconnected the machine harness connector from the Viscus Clutch.
In the harness connector for the Viscus Clutch, place a jumper wire between the contact for terminal 1 (wire G834-PU) and the contact for terminal 2 (wire A209-BK) in the Viscus Clutch harness connector.
Disconnect both the J1 and J2 harness connector from the machine ECM.
At the ECM harness connectors, measure resistance between contact J1-18 (wire A209-BK) and contact J2-24 (wire G834-PU) in the ECM harness connectors. Expected Result:The resistance is less than 5 ohms. Results:
YES - The resistance is less than 5 ohms. Go to Test Step 2.
NO - The resistance is not less than 5 ohms. There is an open circuit in the harness.Repair: Repair or replace the machine harness. Go to Test Step 3.Test Step 2. CHECK THE SENSOR OUTPUT FOR A SHORT CIRCUIT
The disconnect switch and the key start switch remain