FO1974 Force SCREW

Illustration 1 g01184669
Schematic for the engine cooling fan solenoid
Test Step 1. Inspect the Electrical Connectors and the Wiring
Turn the keyswitch to the OFF position.
Illustration 2 g01146374
Left side engine view (typical example)
(1) J1/P1 ECM connector
Illustration 3 g01183942
Engine cooling fan assembly (typical example)
(2) Engine cooling fan speed sensor connector
(3) Cooling fan drive assembly
Thoroughly inspect connectors (1). Also, thoroughly inspect connector (2) that is for the integral components of fan drive (3). Refer to Troubleshooting, "Inspecting Electrical Connectors" for details.
Illustration 4 g01184650
P1 terminal locations for the engine fan control solenoid
(P1-11) Engine fan control solenoid
(P1-69) Solenoid return
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit.
Check the allen head screw for each ECM connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
Check the harness and the wiring for abrasion and for pinch points.Expected Result:All connectors, pins, and sockets are completely coupled and/or inserted. The harness and wiring are free of corrosion, of abrasion, and of pinch points.Results:
OK - The harness and wiring appear to be OK. Proceed to Test Step 2.
Not OK - A problem has been found in the connectors and/or wiring.Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled. Verify that the repair eliminates the problem.STOPTest Step 2. Use Caterpillar Electronic Technician (ET) to check the Actual Speed of the Fan
Turn the keyswitch to the OFF position.
Connect Cat ET to the service tool connector.
Turn the keyswitch to the ON position. Establish communications with the engine ECM.
Access the "Fan Override Test" under the "Diagnostics" menu.
Start the "Fan Override Test" on Cat ET. Set the fan speed to the following speeds:
Minimum allowable speed
Maximum allowable speedNote: These speed settings will vary for different applications of the fan.
Use a 1U-6602 Photo-Tachometer to measure the actual speed of the fan.Expected Result:The actual fan speed is within 50 rpm of the preset value.Results:
OK - The fan speed is correct.Repair: The fan control solenoid is operating correctly. There may be an intermittent electrical problem in a connector or in the harness. If an intermittent problem is suspected, refer to Troubleshooting, "Inspecting Electrical Connectors".If a problem with the fan solenoid is still suspected, proceed to Test Step 3.
Not OK - The actual fan speed is not within 50 rpm of the preset value. There may be a problem with the harness wiring, with the fan control solenoid, or with the ECM. Proceed to Test Step 3.Test Step 3. Check the PWM Signal at the Connector for the Fan Control Solenoid
Turn the keyswitch to the OFF position.
Fabricate two jumper wires that are long enough to be used to measure the control signal at the ECM connector. Crimp connector sockets to one end of each of the jumper wires.
Turn the keyswitch to the ON position.
Use a multimeter to measure the duty cycle of the signal between terminals 4 (fan control solenoid signal) and 3 (solenoid return) on the harness side of the sensor connector.
Start the "Fan Override Test" on Cat ET. Set the "%Bypass" for the fan control solenoid to the following values:
"0% Bypass"
"100% Bypass"When the solenoid is set to "0% Bypass", the duty cycle will be at a minimum.When the solenoid is set to "100% Bypass", the duty cycle will be at a maximum.
Stop the "Fan Override Test".
Turn the keyswitch to the OFF position.Expected Result:The duty cycle of the signal at the connector agrees with the "%Bypass" that is set in Cat ET.Results:
OK - The duty cycle and the "%Bypass" agrees.Repair: The engine harness and the ECM are OK. The fan control solenoid is not responding correctly to the control from the ECM. Replace the fan drive assembly. Verify that the repair resolves the original condition.STOP
Not OK - The duty cycle and the "%Bypass" does not agree. The correct signal is not reaching the connector for the fan control solenoid. There may be a problem with the harness wiring or with the ECM. Proceed to Test Step 4.Test Step 4. Check the Signal at the ECM
Disconnect the J1/P1 ECM connector.
Remove the wires for the fan control solenoid from terminals P1-11 and P1-69 at the ECM connector.
Fabricate two jumper wires that are long enough to be used to measure the control signal at the ECM connector. Crimp connector sockets to one end of each of the jumper wires.
Use a multimeter to measure the duty cycle of the signal between two jumper wires at the J1/P1 ECM connector.
Start the "Fan Override Test" on Cat ET. Set the "%Bypass" for the fan control solenoid to the following values:
"0% Bypass"
"100% Bypass"When the solenoid is set to "0% Bypass", the duty cycle will be at a minimum.When the solenoid is set to "100% Bypass", the duty cycle will be at a maximum.
Stop the "Fan Override Test".
Turn the keyswitch to the OFF position.Expected Result:The duty cycle of the signal agrees with the "%Bypass" that is set in Cat ET.Results:
OK - The duty cycle agrees with the setting for "%Bypass".Repair: The ECM is operating correctly. The problem is in the harness wiring between the ECM and the connector for the fan control solenoid. There may be a problem with a connector. Repair the connectors or wiring and/or replace the connectors or wiring. Verify that the repair resolves the original problem.STOP
Not OK - The duty cycle does not agree with the setting for "%Bypass".Repair: The ECM is not sending the correct signal to the fan control solenoid. Replace the ECM. Refer to Troubleshooting, "Replacing the ECM". Verify that the problem is resolved.STOP