C7.1 Engines and Generator Sets Caterpillar

Cooling Fan Control - Test - Viscous Clutch Fan

Usage:

C7.1 770

This procedure is only applicable to engines with a viscous clutch fan.

Use this procedure to troubleshoot the electrical system if a problem is suspected with the engine fan control solenoid. Use this procedure if one of the diagnostic codes in Table 1 is active.

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Table 1
Diagnostic Trouble Codes for the Cooling Fan Solenoid
J1939 Code	CDL Code	Code Description	Comments
4212-5	291-5	Engine Cooling Fan Solenoid current below normal	The Electronic Control Module (ECM) detects the following conditions: A low current condition in the output from the ECM to the cooling fan solenoid. There are no active 168 diagnostic codes. The Alert lamp will come on. The ECM will log the diagnostic code. This diagnostic code will detect a fault in the circuit for the cooling fan solenoid that is most likely to be an open circuit.
4212-6	291-6	Engine Cooling Fan Solenoid current above normal	The ECM detects the following conditions: A high current condition in the output from the ECM to the cooling fan solenoid. There are no active 168 diagnostic codes. The Alert lamp will come on. The ECM will log the diagnostic code. This diagnostic code will detect a fault in the circuit for the cooling fan solenoid. This problem is most likely to be caused by a high side short to ground or a low side short to power.

The following background information is related to this procedure:

Viscous Clutch Cooling Fan Solenoid

The viscous clutch cooling fan solenoid controls the engagement of the clutch that drives the engine cooling fan. The ECM determines the desired fan speed based on the ATAAC temperature and the coolant temperature. The viscous clutch cooling fan solenoid is controlled by a PWM signal from the ECM.

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Illustration 1	g02484302
View of the connector for the cooling fan solenoid (3) Cooling fan solenoid return (4) Cooling fan solenoid control

During the following procedure, refer to the electrical schematic for the application.

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Table 2
Troubleshooting Test Steps	Values	Results
1. Inspect Electrical Connectors and Wiring A. Thoroughly inspect the P1/J1 ECM connectors and thoroughly inspect the connector for the fan drive assembly. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details. B. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the fan drive assembly. C. Check the screw for the ECM connector for the correct torque of 6 N·m (53 lb in). I. Disable the fan override.	Electrical connectors	Result: All connectors, pins, and sockets are correctly connected and the harness is free of corrosion, abrasion, and pinch points. Proceed to Test Step 2. Result: There is a fault in the connectors and/or the harness. Repair: Repair the connectors or the harness and/or replace the connectors or the harness. Ensure that all the seals are correctly in place and ensure that the connectors are correctly connected. Use the electronic service tool to clear all logged diagnostic codes and then verify that the repair eliminates the fault.
2. Check for Active Diagnostic Codes A. Remove the electrical power from the ECM. B. Verify that the solenoid connectors are free of debris and connected securely. C. Connect the electronic service tool to the diagnostic connector. D. Restore the electrical power to the ECM. E. Select diagnostic tests on the electronic service tool. F. Select the "Override Parameters" screen. G. Activate the fan override. H. Monitor the active diagnostic code screen on the electronic service tool. Check and record any active diagnostic codes. Wait at least 30 seconds in order for the diagnostic code to become active. I. Disable the fan override.	Active Diagnostic Codes	Result: No diagnostic codes are active. The problem may have been related to a faulty connection in the harness. Carefully inspect the connectors and wiring. Refer to Troubleshooting, "Electrical Connectors - Inspect". Result: A 4212-5 (291-5) code is active. Proceed to Test Step 2. Result: A 4212-6 (291-6) code is active. Proceed to Test Step 3.
3. Create a Short Circuit in the Harness at the Solenoid A. Turn the keyswitch to the OFF position. B. Disconnect the connector for the fan drive assembly. C. Fabricate a jumper wire that is long enough to create a short between the terminals of the connector for the fan drive assembly. Crimp connector pins to each end of the jumper wire. D. Install the wire between pin 3 and pin 4 on the harness connector for the fan drive assembly to create a short circuit. E. Turn the keyswitch to the ON position. Wait for 10 seconds. Check for active diagnostic codes on the electronic service tool. E. Activate the fan override. F. Monitor the active diagnostic code screen on the electronic service tool. Check and record any active diagnostic codes. Wait at least 30 seconds in order for the diagnostic code to become active. Disable the fan override. Remove the jumper wire.	Short Circuit	Result: The 4212-5 (291-5) code remains active with the jumper in place. Proceed to Test Step 5. Result: A 4212-6 (291-6) code is active when the jumper wire is installed. A 4212-5 (291-5) code is active when the jumper wire is removed. Repair: Replace the fan drive assembly. Reset all active codes and clear all logged codes. Verify that the fault is resolved. If the fault is still present, contact the Dealer Solutions Network (DSN).
4. Create an Open Circuit at the Solenoid A. Turn the keyswitch to the OFF position. B. Disconnect the connector for the fan drive assembly. C. Turn the keyswitch to the ON position. Wait for 10 seconds. Check for active diagnostic codes on the electronic service tool. D. Activate the fan override. E. Monitor the active diagnostic code screen on the electronic service tool. Check and record any active diagnostic codes. Wait at least 30 seconds in order for the diagnostic code to become active. F. Disable the fan override.	Open circuit	Result: A 4212-6 (291-6) code was active before disconnecting the connector. A 4212-5 (291-5) code became active after disconnecting the connector. Repair: Replace the fan drive assembly. Reset all active codes and clear all logged codes. Verify that the fault is resolved. If the fault is still present, contact the Dealer Solutions Network (DSN). Result: A 4212-6 (291-6) code remains active. There is a short circuit between the harness connector for the engine fan control solenoid and the ECM. Proceed to Test Step 5.
5. Bypass the Wiring Harness A. Turn the keyswitch to the OFF position. B. Disconnect the P1 connector and the fan drive assembly connector. C. Remove the wires for the solenoid control and solenoid return from the P1 connector. Refer to the electrical schematic for the application. D. Remove the wires from pins 3 and 4 on the connector for the fan drive assembly. E. Fabricate two jumper wires that are long enough to reach from the ECM to the fan drive assembly connector. F. Insert one end of a jumper into the solenoid control position on the P1 connector. Insert the other end of the jumper into socket 4 on the harness connector for the fan drive assembly. G. Insert one end of a jumper into the solenoid return position on the P1 connector. Insert the other end of the jumper into socket 3 on the harness connector for the fan drive assembly. H. Reconnect the P1 connector and the fan drive assembly connector. I. Turn the keyswitch to the ON position. Wait for 10 seconds. J. Use the electronic service tool to monitor the "Active Diagnostic Code" screen. Check for a diagnostic code. K. Remove the jumpers and reconnect the wires that were previously removed. Reconnect the connectors.	Wiring bypass	Result: The diagnostic code disappears when the jumper is installed. There is a fault in the wiring harness between the ECM and the cooling fan solenoid connector. Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Reset all active codes and clear all logged codes. Verify that the fault is resolved. If the fault is still present, contact the Dealer Solutions Network (DSN). Result: The diagnostic code is still present with the jumper installed. Contact the Dealer Solutions Network (DSN).