C13, C15, and C18 Engines Troubleshooting – Cooling Fan Speed – Test

System Operation Description:

Use this procedure to troubleshoot the electrical system if a problem is suspected with the cooling fan speed sensor. Also use this procedure if the diagnostic code in Table 1 is active or easily repeated.

Table 1

Diagnostic trouble Codes
Code	Code Description	Comments
E1363(1)	Low Engine Cooling Fan Speed	The code is logged.
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 8.0 ± 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 g02176931
Schematic for the fan speed sensor

Test Step 1. Check the Status of the Engine Fan Speed

 

1. Turn the keyswitch to the OFF position.

 

2. Connect Caterpillar Electronic Technician (ET) to the service tool connector.

 

3. Turn the keyswitch to the ON position.

 

4. Access the “Fan Override Test” under the “Diagnostics” menu.

 

5. Start the “Fan Override Test” on Cat ET. Set the fan speed to 500 rpm.

 

6. Use a 351-8635 Tachometer Kit to determine the actual speed of the fan.

 

7. Compare the engine fan speed that is reported by Cat ET to the actual engine fan speed that is reported by the photo-tachometer.

 

8. Deactivate the “Fan Override Test”.

 

9. Turn the keyswitch to the OFF position.

Results:

 

• The engine fan speed is within ± 50 rpm. –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 Troubleshooting, “Electrical Connectors – Inspect”.

  STOP

   

• The engine fan speed is not within ± 50 rpm. – Proceed to Test Step 2.

Test Step 2. Check the Sensor Supply Voltage at the Sensor Connector

 

1. Turn the keyswitch to the OFF position.

 

2. Disconnect the sensor connector from the wiring harness.

 

3. Turn the keyswitch to the ON position.

 

4. Measure the sensor supply voltage between terminal 2 and terminal 3.

Results:

 

• The supply voltage is reaching the sensor. – Proceed to Test Step 3. 
• The supply voltage is not reaching the sensor. –Repair: Refer to Troubleshooting, “Sensor Supply – Test”.

  STOP

Test Step 3. Check the Signal Frequency at the Sensor Connector

 

1. Turn the keyswitch to the OFF position.

 

2. Remove the wire from terminal 1 on the sensor side of the connector. Connect the sensor connector.

 

3. Turn the keyswitch to the ON position.

 

4. Access the “Fan Override Test” under the “Diagnostics” menu on Cat ET.

 

5. Start the “Fan Override Test” on Cat ET. Set the fan speed to 800 rpm.

 

6. Use a multimeter to measure the frequency between the signal wire from the sensor and engine ground.

 

7. Deactivate the “Fan Override Test”.

 

8. Turn the keyswitch to the OFF position.

 

9. Restore all connectors and wiring to the original configuration.

Results:

 

• The frequency is approximately 80 Hz. –Repair: The engine cooling fan speed sensor is generating the correct signal.Repair the harness or replace the harness.Verify that the problem is resolved.

  STOP

   

• The frequency is not approximately 80 Hz. –Repair: Replace the fan drive assembly.Verify that the problem is resolved.

  STOP