3516E Engine for 994K Wheel Loaders Caterpillar

Cooling Fan Speed - Test

Usage:

994K MM9

Use this procedure to troubleshoot a problem with the cooling fan speed sensor. Also, use this procedure if one of the following diagnostic codes is active or easily repeated.

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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 Reference Torque : Erratic, Intermittent, or Incorrect	The code is logged.
N/A	544-8 Engine Reference Torque : 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 outputs a frequency that is directly proportional to engine speed. The sensor generates a signal pulse for each revolution of the fan.

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Illustration 1	g03848887

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Table 2
Troubleshooting Test Steps	Values	Results
1. Check the Status of the Engine Fan Speed A. Connect Cat^® Electronic Technician (ET) to the service tool connector. B. Use Cat ET to perform the following override: - "Engine Fan Bypass" C. Set the fan speed to 500 rpm. D. Use a 351-8635 Tachometer Kit to determine the actual speed of the fan. E. Compare the engine fan speed that is reported by Cat ET to the actual engine fan speed that is reported by the photo-tachometer. F. Deactivate the "Engine Fan Bypass" override.	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". Verify that the repair eliminated the problem. Result: The engine fan speed is not within ± 50 rpm. Proceed to Test Step 2.
2. Check the Fan Speed Sensor Wiring for an Open Circuit A. Turn the keyswitch to the OFF position. B. Disconnect the fan speed sensor from the wiring harness. C. Disconnect the J1 connector from the ECM. D. Measure the resistance between the following pins: - Pin 32 on the J1 engine harness connector and Pin 2 on the fan speed connector. - Pin 33 on the J1 engine harness connector and Pin 1 on the fan speed connector.	Open Circuit	Result: There were less than 10 ohms of resistance between all the pins. Proceed to Test Step 3. Result: There were more than 10 ohms of resistance between each of the pins. Repair: An open circuit has been detected. Repair or replace the wiring harness. Verify that the repair eliminated the problem. Return to service.
3. Check the Fan Speed Sensor Wiring for a Short Circuit to Ground A. Turn the keyswitch to the OFF position. B. Disconnect the fan speed sensor from the wiring harness. C. Disconnect the J1 connector from the ECM. D. Measure the resistance between the following pins: - Pin 1 on the fan speed connector and a known good ground. - Pin 2 on the fan speed connector and a known good ground.	Short Circuit	Result: There were more than 100 K ohms of resistance between each of the pins and a known good ground. Proceed to Test Step 4. Result: There were less than 100 K ohms of resistance between each of the pins and a known good ground. Repair: A short circuit to ground has been detected. Repair or replace the wiring harness. Verify that the repair eliminated the problem. Return to service.
4. Check the Fan Speed Sensor Wiring for a Pin to Pin Short Circuit A. Turn the keyswitch to the OFF position. B. Disconnect the fan speed sensor from the wiring harness. C. Disconnect the J1 connector from the ECM. D. Measure the resistance between the following pins: - Pin 32 on the J1 engine harness connector and all the other pins in the J1 ECM connector. - Pin 33 on the J1 engine harness connector and all the other pins in the J1 ECM connector.	Short Circuit	Result: There were more than 100 K ohms of resistance between each of the pins and all the pins in the J1 ECM connector. Repair: A failed fan speed sensor has been detected. Replace the fan speed sensor assembly. Verify that the repair eliminated the problem. Result: There were less than 100 K ohms of resistance between each of the pins and all the pins in the J1 ECM connector. Repair: A short circuit has been detected. Repair or replace the wiring harness. Verify that the repair eliminated the problem.

If the procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).