C7.1 Engines and Generator Sets Caterpillar

Cooling Fan Control - Test - Hydraulic Driven Fan

Usage:

C7.1 770

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 solenoid. 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	Engine Cooling Fan Solenoid : 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	Engine Cooling Fan Solenoid : 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.

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.

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 (291-6) code is active. Proceed to Test Step 2. Result: A 4212-5 (291-5) code is active. Proceed to Test Step 3.
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 (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 (291-6) code was active before disconnecting the connector. A 4212-5 (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 (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 (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 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).