SEAL-O-RING 8M4991 - Caterpillar

Probable Causes
Configuration for the communications adapter
Electrical connectors
Communication adapter and/or cables
Electrical power supply to the service tool connector
Electronic service tool and related hardware
Electrical power supply to the Electronic Control Module (ECM)
Data linkRecommended Actions
Start the engine. If the engine will not crank, refer to Troubleshooting, "Engine Will Not Crank". If the engine will not start, refer to Troubleshooting, "Engine Cranks but Will Not Start". If the engine starts, but the ECM will not communicate with the electronic service tool, continue with this procedure.Configuration for the Communications Adapter
Access "Preferences" under the "Utilities" menu on the electronic service tool.
Verify that the correct "Communications Interface Device" is selected.
Verify that the correct port is selected for use by the communication adapter. Note: 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. Electrical Connectors
Check for correct installation of the P1/J1 and P2/J2 ECM connectors and of the diagnostic connector. Refer to Troubleshooting, "Electrical Connectors - Inspect".Communication Adapter and/or Cables
Make sure that the firmware and driver files are the most current files that are available for the type of communication adapter that is being used. If the firmware and driver files do not match, the communication adapter will not communicate with the electronic service tool.
Disconnect the communication adapter and the cables from the diagnostic connector. Reconnect the communication adapter to the diagnostic connector.
Verify that the correct cable is being used between the communication adapter and the diagnostic connector. Refer to Troubleshooting, "Electronic Service Tools".
If the laptop computer is using a Windows operating system, restart the laptop computer in order to eliminate the possibility of a conflict in the software. Electrical Power Supply to the Diagnostic Connector
Verify that battery voltage is present between terminals A and B of the diagnostic connector. If the communication adapter is not receiving power, the LED display on the communication adapter will be blank.Electronic Service Tool and Related Hardware
In order to eliminate the electronic service tool and the related hardware as the fault, connect the electronic service tool to a different engine. If the same fault occurs on a different engine, check the electronic service tool and the related hardware in order to determine the cause of the fault.Electrical Power Supply to the Electronic Control Module (ECM)
Check power to the ECM. Refer to Systems Operation, Testing and Adjusting, "Charging System - Test".Note: If the ECM is not receiving battery voltage, the ECM will not communicate.Data Link
Troubleshoot the data link for possible faults. Refer to Troubleshooting, "Data Link Circuit - Test".