GLASS 2831388 - Caterpillar

Illustration 1 g01253914
Schematic for the fan override switch
Test Step 1. Check the Status of the "Fan Override Switch"
Connect Caterpillar Electronic Technician (ET) to the service tool connector.
Turn the keyswitch to the ON position.
Monitor the status for the "Fan Override Switch" while the fan override switch is toggled to the ON position and the OFF position. The correct status for the "Fan Override Switch" is "On" when the switch is in the ON position. The correct status for the "Fan Override Switch" is "Off" when the switch is in the OFF position.Note: If the status for the "Fan Override Switch" indicates "Not Installed", then the "Fan Override Switch" parameter has not been programmed.
Turn the keyswitch to the OFF position. Expected Result:Cat ET is reporting the correct status for the switch.Results:
OK - Cat ET is reporting the correct status for the switch.Repair: The fan override switch appears to operating correctly at this time. There may be an intermittent electrical problem in the harness or in a connector. If an intermittent problem is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect" for information that is related to troubleshooting intermittent electrical problems.STOP
Not OK - Cat ET is not reporting the correct status for the switch. The ECM is not reading the change in switch status. Proceed to Test Step 2.Test Step 2. Determine the Configuration of the Fan Override Switch
Determine if the fan override switch is wired directly to the ECM, or if the switch position is reported on the J1939 data link.
Verify that the "Fan Override Switch" parameter is programmed to reflect the current wiring for the circuit. Expected Result:The fan override switch is wired directly to the ECM.Results:
OK - The fan override switch is wired directly to the ECM. Proceed to Test Step 3.
Not OK - The fan override switch is not wired directly to the ECM.Repair: The switch position is reported to the ECM via the J1939 data link. Verify that the "Fan Override Switch" parameter is programmed to "J1939 - Body Controller", to "J1939 - Cab Controller", or to "J1939 - Instrument Cluster".Refer to Troubleshooting, "Powertrain Data Link Circuit - Test".STOPTest Step 3. Check the Electrical Connectors and the Wiring
Illustration 2 g01186024
Location of the J1/P1 ECM connectors (typical left side engine view)
Thoroughly inspect the J1/P1 ECM connector, the connectors, and the firewall bulkhead connectors. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Illustration 3 g01253945
Terminal locations at the P1 ECM connector for the fan override switch
(P1-5) AP sensor/switch sensor return
(P1-6) Input No. 6
(P1-7) Input No. 4
(P1-46) Input No. 7
(P1-47) Input No. 5
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the suspect switch circuit.
Check the allen head screw for each of the ECM connectors for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
Check the harness and the wiring for abrasion and pinch points from the battery to the ECM. Then, check the wiring from the keyswitch to the ECM. Expected Result:All connectors,