GUARD AS 9R1290 - Caterpillar

Thoroughly inspect ECM connector J1/P1, ECM connector J2/P2, and all other connectors in the wiring harness. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Illustration 3 g02593596
P2 terminals that are associated with the cooling fan speed (P2-56) 8V digital supply (P2-70) Engine fan speed
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P1 terminals that are associated with the cooling fan speed (P1-60) Digital return
Perform a 45 N (10 lb) pull test on each of the wires that are associated with the Cat Data Link.
Check the allen head screw on each ECM connector for the proper torque. Also, check the allen head screw on the customer connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.Expected Result:All connectors, pins, and sockets are inserted and coupled. The harness and wiring are free of corrosion, of abrasion, and of pinch points.Results:
OK - The harness and connectors appear to be OK. Proceed to Test Step 2.
Not OK - There is a problem with 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 coupled. Verify that the repair eliminates the problem.STOPTest Step 2. Check the Status of the Engine Fan Speed with Caterpillar Electronic Technician (ET)
Turn the keyswitch to the OFF position.
Connect Cat ET to the service tool connector.
Turn the keyswitch to the ON position.
Access the "Fan Override Test" under the "Diagnostics" menu.
Start the "Fan Override Test" on Cat ET. Set the fan speed to 800 rpm.
Use a 1U-6602 Photo-Tachometer to determine the actual speed of the fan.
Compare the engine fan speed that is reported by Cat ET to the actual engine fan speed that is reported by the photo-tachometer.
Deactivate the "Fan Override Test".
Turn the keyswitch to the OFF position.Expected Result:The actual fan speed is within 50 rpm of the engine fan speed that is reported by Cat ET.Results:
OK - The engine fan speed is within the desired rpm range.Repair: The sensor 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, "Electrical Connectors - Inspect".STOP
Not OK - The engine fan speed is not within the desired rpm range. Proceed to Test Step 4.Test Step 3. Check the Digital Sensor Supply Voltage at the Sensor Connector
Disconnect the connector for the engine cooling fan speed sensor.
Turn the keyswitch to the ON position.
Measure the voltage across terminal A (+8 V digital supply) and terminal B (sensor return).
Turn the keyswitch to the OFF position.Expected Result:The digital sensor supply voltage is 8.0 0.5 VDC.Results:
OK - The supply voltage is reaching the sensor. Proceed to Test Step 5.
Not OK - The supply voltage is not reaching the sensor. Proceed to Test Step 7.Test Step 4. Check the Resistance of the Cooling Fan Resistor
Remove the electrical power from the ECM.
Disconnect the