The Diagnostic Trouble Code (DTC) U1073 in a Mitsubishi vehicle indicates a communication error within the Controller Area Network (CAN) bus system, specifically a “bus off” condition related to the ETACS-ECU (Electronic Time and Alarm Control System). This guide provides a comprehensive troubleshooting procedure for addressing this issue.
Understanding the U1073 code is crucial for effective diagnosis. This code signifies that the ETACS-ECU has lost communication with the CAN bus and subsequently re-established communication after the ignition switch was cycled. This disruption can lead to various malfunctions in the vehicle’s electronic systems controlled by the ETACS-ECU. A common cause is a problem with the CAN bus wiring, such as damaged wires, loose connectors, or corroded terminals.
Diagnosing DTC U1073
The following steps outline a systematic approach to diagnosing and resolving the U1073 DTC:
Step 1: CAN Bus Diagnostics with M.U.T.-III
The first step involves utilizing the Mitsubishi Motors Universal Tester III (M.U.T.-III) to perform a comprehensive diagnosis of the CAN bus lines. This diagnostic tool allows for in-depth analysis of communication signals and potential errors within the network. The M.U.T-III will guide you through specific tests to pinpoint the source of the problem.
If the M.U.T.-III indicates a problem with the CAN bus lines: Repair the identified issue, referring to the relevant section in the Mitsubishi service manual (Group 54C – Troubleshooting).
If the M.U.T.-III indicates no problems with the CAN bus lines: Proceed to Step 2.
Step 2: DTC Reset Verification
After addressing any CAN bus issues or if none were found, the next step is to verify if the DTC U1073 can be reset:
- Erase the DTC: Use the M.U.T.-III to clear the U1073 code from the ETACS-ECU’s memory.
- Cycle the Ignition: Turn the ignition switch from the “OFF” (LOCK) position to the “ON” position.
- Check for DTC: Use the M.U.T.-III to check if the U1073 code has been reset.
If the DTC U1073 reappears: Replace the ETACS-ECU and register the ID codes, as outlined in the Mitsubishi service manual. Then proceed to Step 3.
If the DTC U1073 does not reappear: The problem might be intermittent, such as a loose connection or an open circuit. Refer to Group 00 of the Mitsubishi service manual for guidance on troubleshooting intermittent malfunctions.
Step 3: Final DTC Reset Verification
This step is a final confirmation to ensure the issue has been resolved:
- Erase the DTC: Clear any existing DTCs from the ETACS-ECU using the M.U.T.-III.
- Cycle the Ignition: Turn the ignition switch from “OFF” to “ON.”
- Check for DTC: Verify that the DTC U1073 does not reappear.
If the DTC U1073 reappears: Return to Step 1 and re-evaluate the entire diagnostic process.
If the DTC U1073 does not reappear: The troubleshooting procedure is complete, and the U1073 issue should be resolved.
Conclusion
Troubleshooting the DTC U1073 in a Mitsubishi vehicle requires a systematic approach, utilizing the M.U.T.-III diagnostic tool and following the outlined procedure. By carefully inspecting the CAN bus lines, resetting the DTC, and potentially replacing the ETACS-ECU, you can effectively address this communication error and restore proper vehicle functionality. Always consult the specific Mitsubishi service manual for your vehicle model for detailed instructions and wiring diagrams.
