Posted on October 27, 2020 C7 and C9 Industrial Engines Troubleshooting – ECM Does Not Communicate with Other Modules Probable Causes Wiring and/or electrical connectors Cat Data Link CAN data link (if equipped) Electronic Control Module (ECM) Recommended Actions Note: The procedures have been listed in order of probability. Complete the procedures in the order of the listed test steps. Table 1 Troubleshooting Test Steps Values Results 1. Check for correct installation of the connectors for the ECM J1/P1, J2/P2, and J3/P3. Refer to the diagnostic functional test Troubleshooting, “Electrical Connectors – Inspect” ECM Result: Connectors are installed incorrectly. Repair: Correct the installation issue. Return to service. Result: Connectors are installed correctly. Proceed to Test Step 2 2. Connect Cat ® Electronic Technician (Cat ET) to the service tool connector. Cat ET Result: Cat ET will not communicate with the ECM. Proceed to troubleshooting without a diagnostic code Troubleshooting, “Electronic Service Tool Will Not Communicate with ECM.” Result: Cat ET communicates with the ECM. Proceed to Test Step 3. 3. Troubleshoot the Cat Data Link for possible problems. Cat Data Link Result: Cat Data Link does not connect. Refer to the diagnostic functional test Troubleshooting, “Cat Data Link Circuit – Test”. Result: Cat Data Link connects. Proceed to Test Step 4. 4. Troubleshoot the CAN Data Link (if equipped) for possible problems. CAN Data Link Result: CAN Data Link does not connect. Refer to the diagnostic functional test Troubleshooting, “CAN Data Link Circuit – Test”. Result: CAN Data Link connects. Return to service.