C1.7 and C2.2 Industrial Engine Caterpillar


Relay - Test - Fan Drive Relay

Usage:

C1.7 G34
This procedure covers the following diagnostic codes:

Table 1
Diagnostic Trouble Codes for the Fan Drive Relay 
J1939 Code  Code Description  Comments 
1071-3  Cooling Fan Drive Output : Voltage Above Normal  The Electronic Control Module (ECM) detects a high voltage condition (open circuit) in the fan drive relay control circuit. 
1071-4  Cooling Fan Drive Output : Voltage Below Normal  The Electronic Control Module (ECM) detects a low voltage condition (short circuit) in the fan drive relay control circuit. 
Follow the troubleshooting procedure to identify the root cause of the fault. 


Illustration 1g06100283
Schematic for the fan drive relay


Illustration 2g06028408

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

Table 2
Troubleshooting Test Steps  Values  Results 

1. Inspect Electrical Connectors and Wiring

A. Inspect the terminals on the fan drive relay. Refer to Troubleshooting, "Electrical Connector - Inspect" for details.

B. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connectors that are associated with the fan drive relay.

C. Check the harness for abrasion and pinch points from the fan drive relay back to the ECMs.
 

Loose connection or damaged wire
 

Result: There is a fault in a connector or the wiring.

Repair: Repair any faulty connectors or replace the wiring harness. Ensure that all the seals are properly in place and ensure that the connectors are correctly coupled.

Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault.

Result: All connectors, pins, and sockets are correctly coupled and/or inserted. The harness is free of corrosion, abrasion, and pinch points. The fuses are not blown.

Proceed to Test Step 2.
 

2. Check for Active Diagnostic Codes

A. Connect the electronic service tool to the diagnostic connector.

B. Turn the keyswitch to the ON position.
Note: Do not start the engine.

C. Use the electronic service tool to check for active diagnostic codes.

D. Turn the keyswitch to the OFF position.
 

Diagnostic codes
 

Result: Diagnostic code 1071-3 is active or recently logged.

Proceed to Test Step 3.

Result: Diagnostic code 1071-4 is active or recently logged.

Proceed to Test Step 6.
 

3. Check the Supply Voltage at the Fan Drive Relay Connector

A. Remove the fan drive relay.

B. Measure the voltage between Test Point 2 on the relay connector and a suitable ground.

C. Turn the keyswitch to the OFF position.

D. Install the fan drive relay.
 

At least 11 VDC
 

Result: The voltage is not within the expected range.

Repair: Repair or replace the supply wiring to the fan drive relay.

Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault.

Result: The voltage is within the expected range.

Proceed to Test Step 4.
 

4. Check the Return Wire from the Fan Drive Relay to the Engine ECM

A. Turn the keyswitch to the OFF position.

B. Remove the fan drive relay.

C. Disconnect the P2 connector from the engine ECM.

D. Measure the resistance between Test Point 1 on the fan drive relay connector and P2:77.

E. Connect the P2 connector to the engine ECM.

F. Install the fan drive relay.
 

Less than 2.0 Ohms
 

Result: The measured resistance is more than 2.0 Ohms.

Repair: Repair or replace the return wiring from the fan drive relay.

Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault.

Result: The measured resistance is less than 2.0 Ohms.

Proceed to Test Step 5.
 

5. Check the Fan Drive Relay Solenoid for an Open Circuit

A. Verify that the keyswitch is in the OFF position.

B. Remove the fan drive relay.

C. Measure the resistance between Test Points 1 and 2 on the fan drive relay. Refer to Illustration 2.

D. Install the fan drive relay.
 

81 Ohms to 113 Ohms
 

Result: The measured resistance is more than 81 Ohms to 133 Ohms.

Repair: Install a replacement fan drive relay.

Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault.

Result: The measured resistance is within 81 Ohms to 133 Ohms.

Contact the Dealer Solutions Network (DSN).
 

6. Check the Wiring for a Short Circuit

A. Turn the keyswitch to the OFF position.

B. Remove the fan drive relay.

C. Disconnect the P2 connector from the engine ECM.

D. Check the resistance between P2:77 and all other pins on the P2 connector for the engine ECM.

E. Reconnect the P2 connector to the engine ECM.

F. Install the fan drive relay.
 

More than 1k Ohm
 

Result: One or more resistance measurements are less than 1k Ohm.

Repair: Repair or replace the wiring.

Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault.

Result: All resistance measurements are more than 1k Ohm.

Proceed to Test Step 7.
 

7. Check the Fan Drive Relay Solenoid for a Short Circuit

A. Verify that the keyswitch is in the OFF position.

B. Remove the fan drive relay.

C. Measure the resistance between Test Points 1 and 2 on the fan drive relay. Refer to Illustration 2.

D. Install the fan drive relay.
 

81 Ohms to 113 Ohms
 

Result: The measured resistance is less than 81 Ohms to 133 Ohms.

Repair: Install a replacement fan drive relay.

Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault.

Result: The measured resistance is within 81 Ohms to 133 Ohms.

Proceed to Test Step 8.
 

8. Perform a Fan Drive Relay Override Test

A. Turn the keyswitch to the ON position.

B. Use the electronic service tool to perform the Fan Drive Relay Override Service Test.

C. Check the operation of the cooling fan.

D. Stop the Fan Drive Relay Override Service Test.

E. Turn the keyswitch to the OFF position.
 

Battery voltage
 

Result: The cooling fan operates correctly.

Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault.

Result: The cooling fan does not operate correctly.

Contact the Dealer Solutions Network (DSN).
 

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