HOSE AS 3135545 - Caterpillar

Table 1
Diagnostic Codes for Cooling Fan Control
J1939 Code CDL Code Code Description
(code descriptions may vary) Comments
- 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. The ECM monitors engine coolant temperature, intake manifold air temperature, and hydraulic oil temperature. The ECM monitors the sensors in order to determine the correct speed for the engine cooling fan.The cooling fan bypass solenoid prevents operation of the fan when the engine is cold. During the following procedure, refer to the electrical schematic for the application.Complete the procedure in the order in which the steps are listed.
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 connector is 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 1076-6 code is active at this time.
Proceed to Test Step 2.
Result: A 1076-5 code is active at this time.
Proceed to Test Step 3.
2. 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