61998 Mercruiser SPACER, CIRCUIT BREAKER ATTACHHING SCREW(

Table 1
J1939 Code and Description CDL Code and Description Comments
1639-17
Fan Speed : Low - least severe (1) E1363 (1)
Low Engine Cooling Fan Speed The code is logged.
N/A 544-2
Engine Cooling Fan Speed Sensor : Erratic, Intermittent, or Incorrect The code is logged.
N/A 544-8
Engine Cooling Fan Speed Sensor : Abnormal Frequency, Pulse Width, or Period 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.The engine cooling fan speed sensor receives a supply voltage of 5.0 0.5 VDC from the ECM. The sensor outputs a frequency that is directly proportional to fan speed. The sensor generates a signal pulse for each revolution of the fan. The output frequency varies between 5 Hz to 180 Hz over the speed range between 50 rpm and 1800 rpm.
Illustration 1 g03011039
Schematic for the fan speed sensor "3 Pin Connector"
Illustration 2 g06124085
Schematic for the fan speed sensor "6 Pin Connector"
Illustration 3 g06414089
Schematic for the Viscous Clutch "6 Pin Connector"
Table 2
Troubleshooting Test Steps Values Results
1. Check the Status of the Engine Fan Speed
A. Turn the keyswitch to the OFF position.
B. Connect Cat® Electronic Technician (ET) to the service tool connector.
C. Turn the keyswitch to the ON position.
D. Access the "Fan Override Test" under the "Diagnostics" menu.
E. Start the "Fan Override Test" on Cat ET. Set the fan speed to 800 rpm.
F. Use a 351-8635 Tachometer Kit to determine the actual speed of the fan.
G. Compare the engine fan speed that is reported by Cat ET to the actual engine fan speed that is reported by the photo-tachometer.
H. Deactivate the "Fan Override Test".
I. Turn the keyswitch to the OFF position.
Fan Speed
Result: The engine fan speed is within 50 rpm.
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 Troubleshooting, "Electrical Connectors - Inspect".
Result: The engine fan speed is not within 50 rpm.
Proceed to Test Step 2.
2. Check the Sensor Supply Voltage at the Sensor Connector
A. Turn the keyswitch to the OFF position.
B. Disconnect the sensor connector from the wiring harness.
C. Turn the keyswitch to the ON position.
D. Measure the voltage between the fan speed sensor supply pin and the ground pin.
Note: Some fan speed sensors use a 5V power supply and some use an 8V power supply. Refer to the appropriate schematic for the correct pins.
Supply Voltage
Result: The supply voltage is reaching the sensor.
Proceed to Test Step 3.
Result: The supply voltage is not reaching the sensor.
Repair: Refer to Troubleshooting, "Sensor Supply - Test".
3. Check the Signal Frequency at the Sensor Connector
A. Turn the keyswitch to the OFF position.
B. Remove the wire from terminal 1 on the sensor side of the connector. Connect the sensor connector.
C. Turn the keyswitch to the ON position.
D. Access the "Fan Override Test" under the "Diagnostics" menu on Cat ET.
E. Start the "Fan Override Test" on Cat ET. Set the fan speed to 800 rpm.
F. Use a multimeter to measure the frequency between the signal wire from the sensor and engine ground.
G. Deactivate the "Fan Override Test".
H. Turn the keyswitch to the OFF position.
I. Restore all connectors and wiring to the original configuration.
Sensor Frequency
Result: The frequency is approximately 80 Hz.
Note: Large Hydraulic Excavators use a frequency of 27Hz
The engine cooling fan speed sensor is generating the correct signal.
Repair: Repair the harness or replace the harness.
Verify that the problem is resolved.
Note: Large Hydraulic Excavators use a frequency of 27Hz
Result: The frequency is not approximately 80 Hz.
Repair: Replace the fan drive assembly.
Verify that the problem is resolved.