<ul> <li><b>Engine Light ON (or Service Engine Soon Warning Light)</b>: The engine light illuminates on the dashboard, indicating a communication issue with the Differential Control Module Front. This can be caused by a faulty module, wiring issues, or a problem with the CAN bus network.</li> <li><b>Loss of Traction Control</b>: The vehicle may experience a loss of traction control functionality, which can be due to the inability of the Differential Control Module to communicate with other control units.</li> <li><b>Erratic Shifting</b>: Transmission may shift erratically or not at all, as the Differential Control Module plays a role in managing power distribution to the wheels.</li> <li><b>ABS Warning Light</b>: The ABS warning light may also illuminate, indicating a potential issue with the vehicle's stability and braking systems, often linked to communication failures with the Differential Control Module.</li> </ul>

<ul><li>The Differential Control Module Front may be faulty, leading to a loss of communication.</li><li>An open or shorted harness in the Differential Control Module Front can disrupt the communication signal.</li><li>Poor electrical connections in the Differential Control Module Front circuit can cause intermittent or complete communication failure.</li></ul>

<ul> <li><b>Initial Scan</b>: Perform a full system scan using an OBD-II scanner to confirm the presence of DTC U0135 and check for any other related codes.</li> <li><b>Inspect Wiring and Connectors</b>: Visually inspect the wiring and connectors leading to the Differential Control Module (DCM). Look for signs of damage, corrosion, or loose connections.</li> <li><b>Check Power and Ground</b>: Verify that the DCM is receiving proper power and ground. Use a multimeter to check the voltage and ground connections at the module.</li> <li><b>Test CAN Bus Communication</b>: Use an oscilloscope or a specialized scan tool to check the CAN bus communication lines for proper signals. Ensure there are no breaks or shorts in the CAN bus wiring.</li> <li><b>Module Reset</b>: Attempt to reset the DCM by disconnecting the battery for a few minutes or using a scan tool to perform a module reset. Re-scan for codes after the reset.</li> <li><b>Replace Differential Control Module</b>: If all previous steps do not resolve the issue, consider replacing the Differential Control Module. Ensure the new module is properly programmed and configured for the vehicle.</li></ul>

<p>The DTC code U0135 indicates a <b>critical</b> issue with the communication between the vehicle's main control module and the Differential Control Module Front. This can lead to severe drivability issues, including loss of traction control and stability. Immediate action is required to diagnose and repair the communication fault to prevent potential safety hazards.</p>