HARNESS AS-SWITCH 3655935 - Caterpillar

Probable Causes
Configuration for the communications adapter
J1/P1 connectors for the Engine Control Module (ECM)
Communication adapter and/or cables
Electrical power supply to the service tool connector
Caterpillar Electronic Technician (ET) and related hardware
Electrical power supply to the ECM
Override switches
ATA data link
J1939 data linkRecommended Actions
Attempt to start the engine. If the engine starts, but the ECM will not communicate with the Cat ET, continue with this procedure. If the engine will not start, refer to Troubleshooting, "Engine Cranks but Will Not Start". If the engine will not crank, refer to Troubleshooting, "Engine Will Not Crank". Configuration for the Communications Adapter
Access "Preferences" under the "Utilities" menu on Cat ET.
Verify that the correct "Communications Interface Device" is selected.
Verify that the correct "Port" is selected for use by the communication adapter. The most commonly used port is "COM 1".
Check for any hardware that is utilizing the same port as the communications adapter. If any devices are configured to use the same port, exit or close the software programs for that device. J1/P1 ECM Connectors
Check the J1/P1 ECM connectors for the following problems:
Proper torque
Cleanliness of the terminals
Wires and terminals are properly installed into the connector.Refer to Troubleshooting, "Electrical Connectors - Inspect" for additional information.Communication Adapter and/or Cables
Verify that the correct cable is being used between the communication adapter and the service tool connector. Refer to Troubleshooting, "Electronic Service Tools".If you are using a 171-4401 Communication Adapter As, ensure that the firmware and software files for the communication adapter are the most current files that are available. If the firmware and software do not match, the communication adapter will not communicate with Cat ET.Electrical Power Supply to the Service Tool Connector
Verify that battery voltage is present between terminals A and B of the service tool connector. If the communication adapter is not receiving power, the communication adapter's display will be blank.Cat ET and Related Hardware
In order to eliminate Cat ET and the related hardware as the problem, connect Cat ET to a different engine. If the same problem occurs on a different engine, check Cat ET and the related hardware in order to determine the cause of the problem.Electrical Power Supply to the ECM
If the ECM is not receiving battery voltage, the ECM will not communicate. Check the electrical power to the ECM. Refer to Troubleshooting, "Ignition Key Switch Circuit and Battery Supply Circuit - Test".Override Switches
Verify that there are no aftermarket devices that are preventing battery voltage from reaching the ECM.Some type of override switch is interrupting the power to the ECM if the following conditions are true:
Communication occurs when the engine is running.
No communication occurs when the engine is not running and the keyswitch is ON.Perform the following procedure:
Turn the keyswitch to the OFF position.
Disconnect Cat ET.
Turn the keyswitch to the ON position.
Connect Cat ET. This may solve the communication problem.ATA Data Link
Troubleshoot the ATA data link for possible problems. Refer to Troubleshooting, "ATA (SAE J1587 / J1708) Data Link Circuit - Test".J1939 Data Link
Troubleshoot the J1939 data link for possible problems. Refer to Troubleshooting,