0385195 JOHNSON ARM & SHAFT ASSY, Long

Table 1
Diagnostic Codes Table    
CDL Code and Description     Conditions which Generate the Code     System Response    
544-2 Engine Cooling Fan Speed Sensor : Erratic, Intermittent, or Incorrect     The signal from the fan speed sensor is intermittent or the signal has been lost.     The code is logged.    
544-8 Engine Cooling Fan Speed Sensor:Abnormal Frequency, Pulse Width, or Period     The signal from the fan speed sensor is abnormal.     The code is logged.    The engine cooling fan speed sensor provides a signal to the Electronic Control Module (ECM). The ECM controls fan speed by varying the current to the fan control solenoid.
Illustration 1 g02154664
Location of the cooling fan speed sensor (1) Cooling fan speed sensor (2) ResistorThe engine cooling fan speed sensor receives a supply voltage of 8.0 0.5 VDC from the ECM. The sensor outputs a frequency that is directly proportional to fan speed. There is a connector for a 4,700 Ohm pull-up resistor spliced into the harness near the sensor. The resistor is mounted near the cooling fan toward the front of the engine.The sensor generates a signal pulse for each revolution of the fan. The output frequency varies between 0.83 Hz to 30 Hz over the speed range between 50 rpm and 1800 rpm.
Illustration 2 g03612318
Schematic for the cooling fan speed sensorTest Step 1. Inspect the Electrical Connectors and the Wiring
Remove the electrical power from the ECM.
Illustration 3 g02220433
Location of the ECM connectors (3) J1/P1 ECM connectors
Thoroughly inspect the connectors for sensor (1) and resistor (2) . Also, thoroughly inspect ECM connector (3) . Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Illustration 4 g02154896
P1 ECM connector (P1-4) 8 V supply (P1-5) Return (P1-32) Cooling fan speed
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit.
Check the allen head screw for each ECM connectors for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Check the harness and the wiring for abrasion and for pinch points.Expected Result:All connectors, pins, and sockets are coupled and inserted and the harness and wiring are free of corrosion, of abrasion, and of pinch points.Results:
OK - The harness and connectors appear to be OK. Proceed to Test Step 2.
Not OK - There is a problem with the connectors and/or wiring.Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are coupled. Verify that the repair eliminates the problem.STOPTest Step 2. Check the Status of the Engine Fan Speed with Caterpillar Electronic Technician (ET)
Remove the electrical power from the ECM.
Connect Cat ET to the service tool connector. Start Cat ET.
Restore the electrical power to the ECM.
Access the "Engine Fan Bypass" under the "Diagnostics" menu.
Start the "Engine Fan Bypass" on Cat ET. Set the fan speed to 800 rpm.
Use a 1U-6602 Photo-Tachometer to determine the actual speed of the fan.
Compare the engine fan speed that is reported by Cat ET to the actual engine fan speed that is reported by the photo-tachometer.
Deactivate the "Engine Fan Bypass".Expected Result:The actual fan speed is within 50 rpm of the engine fan speed that is reported by Cat ET.Results:
OK - The engine fan speed is within the desired rpm range.Repair: The sensor is operating correctly. There may be an intermittent electrical problem in a connector or in the harness. If an intermittent problem is suspected, refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".STOP
Not OK - The engine fan speed is not within the desired rpm range. Proceed to Test Step 3.Test Step 3. Check the Supply Voltage at the Connector for the Speed Sensor
Remove the electrical power from the ECM.
Disconnect the connector for the engine cooling fan speed sensor.
Restore the electrical power to the ECM.
Measure the sensor supply voltage on the harness side of the connector for the engine cooling fan speed sensor. Connect the test leads between terminal A (8 V supply) and terminal B (digital return).Expected Result:The voltage is 8.0 0.4 VDC.Results:
OK - The voltage is 8.0 0.4 VDC. The supply voltage is reaching the sensor connector. Proceed to Test Step 4.
Not OK - The voltage is not 8.0 0.4 VDC.Repair: The supply voltage is not reaching the sensor. Refer to the diagnostic functional test Troubleshooting, "Sensor Supply - Test".STOPTest Step 4. Check the Resistance of the Cooling Fan Resistor
Remove the electrical power from the ECM.
Disconnect the cooling fan resistor at the harness connector for the resistor.
Measure the resistance of the resistor.Expected Result:The resistance of the cooling fan resistor is 4700 50 Ohm.Results:
OK - The resistance of the resistor is 4700 50 Ohm. The resistance of the resistor is within specifications. Reinstall the resistor. Proceed to Test Step 5
Not OK - The resistance of the resistor is not 4700 50 Ohm.Repair: There is a problem with the cooling fan resistor. Replace the resistor.Verify that the original problem has been resolved.STOPTest Step 5. Check the Signal Frequency for the Engine Cooling Fan Speed Sensor at the Sensor Connector
Remove the electrical power from the ECM.
Remove the signal wire terminal C (engine fan speed) on the sensor side of the connector for the engine cooling fan speed sensor. Connect the sensor connector.
Restore the electrical power to the ECM.
Access the "Engine Fan Bypass" under the "Diagnostics" menu on Cat ET.
Start the "Engine Fan Bypass" on Cat ET. Set the fan speed to 800 rpm.
Use a multimeter to measure the frequency between the signal wire from the sensor and engine ground.
Deactivate the "Engine Fan Bypass".
Remove the electrical power from the ECM.
Restore all connectors and wiring to the original configuration.Expected Result:The freq