C4.4 and C6.6 Engines Caterpillar

Cooling Fan Control - Test

Usage:

C4.4 448

This procedure is only applicable to engines with a hydraulic driven fan.

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

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Table 1
Diagnostic Codes for Cooling Fan Control
J1939 Code	CDL Code	Code Description (code descriptions may vary)	Comments
4212–5	291-5	Fan Drive Bypass Command Status : Current Below Normal	The Electronic Control Module (ECM) detects an open circuit in the circuit for the engine fan control solenoid. The ECM sends minimum current to the fan control solenoid. The code is logged.
4212–6	291-6	Fan Drive Bypass Command Status : Current Above Normal	The ECM detects a short circuit to ground in the circuit for the engine fan control solenoid. The ECM sends minimum current to the fan control solenoid. The code is logged.
-	1076-5	Engine Cooling Fan Bypass Solenoid : Current Below Normal	The Electronic Control Module (ECM) detects an open circuit in the circuit for the engine cooling fan bypass solenoid. The ECM sends minimum current to the fan control solenoid. The code is logged.
-	1076-6	Engine Cooling Fan Bypass Solenoid : Current Above Normal	The ECM detects a short circuit to ground in the circuit for the engine cooling fan bypass solenoid. The ECM sends minimum current to the fan bypass solenoid. The code is logged.
-	3964-4	Engine Cooling Fan Bypass Relay : Voltage Below Normal	The ECM detects an open circuit in the circuit for the engine cooling fan bypass relay. The ECM sends minimum current to the fan bypass solenoid. The code is logged.

The ECM monitors engine coolant temperature, intake manifold air temperature, and hydraulic oil temperature. The ECM monitors the sensors to determine the correct speed for the engine cooling fan.

The ECM controls the speed of the fan by controlling the current to the engine fan control solenoid. The engine fan control solenoid controls the amount of pressure to the fan motor by allowing oil to bypass the fan motor. The fan pump drives the fan. When the ECM outputs minimum current to the engine fan control solenoid, less oil is bypassed. The fan motor will now drive the fan at a higher rpm. When the ECM outputs maximum current to the engine fan control solenoid, more oil is bypassed. The fan motor will now drive the fan at a lower rpm.

If the ECM detects a system fault, the ECM provides minimum current to the solenoid. Minimum current ensures a maximum fan speed while the fault condition exists.

An override is available in the electronic service tool. The override allows the fan to be manually changed from the minimum to the maximum rpm.

The cooling fan bypass relay and solenoid prevent operation of the fan when the engine is cold. When the engine has warmed up, the solenoid will open the valve to allow hydraulic pressure to flow to the fan motor.

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

Complete the procedure in the order in which the steps are listed.

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Table 2
Troubleshooting Test Steps	Values	Results
1. 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 4212-6 or 291-6 code is active currently. Proceed to Test Step 2. Result: A 4212-5 or 291-5 code is active currently. Proceed to Test Step 3. Result: A 1076-6 code is active currently. Proceed to Test Step 4. Result: A 1076-5 code is active currently. Proceed to Test Step 5. Result: A 3964-4 code is active currently. Proceed to Test Step 6.
2. Disconnect the Connector for the Engine Fan Control Solenoid in Order to Create an Open Circuit A. Remove the electrical power from the ECM. B. Disconnect the connector for the engine fan control solenoid. C. Restore the electrical power to the ECM. 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.	Short circuit	Result: A 4212-6 or 291-6 code remains active. There is a short circuit between the harness connector for the engine fan control solenoid and the ECM. 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. Result: A 4212-6 or 291-6 code was active before disconnecting the connector. A 4212-5 or 291-5 code became active after disconnecting the connector. Repair: Replace the engine fan control solenoid. 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).
3. Create a Short at the Connector for the Engine Fan Control Solenoid A. Remove the electrical power from the ECM. B. Fabricate a jumper wire that is long enough to create a short between the terminals of the connector for the engine fan control solenoid. Crimp connector pins to each end of the jumper wire. C. Install the jumper wire between terminal 1 (engine fan control solenoid) and terminal 2 (solenoid return) on the harness side of the connector. D. Restore the electrical power to the ECM. 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.	Open Circuit	Result: The 4212-5 or 291-5 code remains active with the jumper in place. 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. Result: A 4212-6 or 291-6 code is active when the jumper wire is installed. A 4212-5 or 291-5 code is active when the jumper wire is removed. Repair: Replace the engine fan control solenoid. 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. Disconnect the Connector for the Engine Fan Bypass Solenoid in Order to Create an Open Circuit Note: The following procedure must be done on a cold engine. A. Remove the electrical power from the ECM. B. Disconnect the connector for the engine fan bypass solenoid. C. Restore the electrical power to the ECM. 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.	Short circuit	Result: A 1076-6 code remains active. There is a short circuit between the harness connector for the engine fan bypass solenoid and the ECM. 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. Result: A 1076-6 code was active before disconnecting the connector. A 1076-5 code became active after disconnecting the connector. Repair: Replace the engine fan bypass solenoid. 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).
5. Create a Short at the Connector for the Engine Fan Control Solenoid Note: The following procedure must be done on a cold engine. A. Remove the electrical power from the ECM. B. Fabricate a jumper wire that is long enough to create a short between the terminals of the connector for the engine fan bypass solenoid. Crimp connector pins to each end of the jumper wire. C. Install the jumper wire between terminal 1 (engine fan bypass solenoid) and terminal 2 (solenoid return) on the harness side of the connector. D. Restore the electrical power to the ECM. 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.	Open Circuit	Result: The 1076-5 code remains active with the jumper in place. 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. Result: A 1076-6 code is active when the jumper wire is installed. A 1076-5 code is active when the jumper wire is removed. Repair: Replace the engine fan bypass solenoid. 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).
6. Check the Wiring Between the ECM and the Fan Bypass Relay for an Open Circuit A. Turn the keyswitch to the OFF position. B. Disconnect the fan bypass relay. Disconnect the J1 connector from the ECM. C. Use a multimeter to measure the resistance between J1:13 and terminal 5 on the harness connector for the relay.	Less than 2 Ohms	Result: The resistance measurement is greater than 2 Ohms. Repair: The fault is in the wiring between the fan bypass relay and the ECM. Repair the faulty wiring or replace the faulty wiring. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: The resistance measurement is less than 2 Ohms. Proceed to Test Step 7.
7. Check the Wiring Between the Relay and the ECM for a Short Circuit A. Turn the keyswitch to the OFF position. B. Disconnect the P1 connector. C. Inspect the P1/J1 connector. Refer to Troubleshooting, "Electrical Connectors - Inspect". D. Disconnect the connector for the fan bypass relay. E. Measure the resistance between P1:13 and all other pins on the P1 connector. F. Measure the resistance between P1:13 and ground.	Greater than 1 k Ohm	Result: At least one of the resistance measurements is less than 1 k Ohm. The fault is in the wiring between the fan bypass relay and the ECM. Repair: Repair the faulty wiring or replace the faulty harness. Turn the keyswitch to the ON position. Do not start the engine. Check for active diagnostic codes. Check for a 3964-4 diagnostic code. Confirm that the fault has been eliminated. Result: All resistance measurements are greater than 1 k Ohm. Proceed to Test Step 8.
8. Check the Power Supply to the Relay Connector A. Disconnect the connector for the fan bypass relay. B. Measure the voltage between terminal 2 on the harness connector for the relay and a suitable ground.	Battery voltage	Result: There is no battery voltage at terminal 2 on the harness connector. Repair: Check the power supply wiring to the fan bypass relay. Make any necessary repairs. Result: Battery voltage is present at terminal 2 on the harness connector. Repair: Install a replacement fan bypass relay. Use the electronic service tool to activate the fan bypass override. Check for a 3964-4 diagnostic code. If diagnostic code 3964-4 is not active, return the unit to service. If a 3964-4 diagnostic code is active, contact the Dealer Solutions Network (DSN).