Lost Communication With Vehicle Dynamics Control Module
Your car's main computer lost its connection to the stability control module, like a phone losing signal from a tower. This prevents the vehicle from communicating brake and steering corrections needed for safe handling.
The ECM monitors CAN bus communication with the Vehicle Dynamics Control (VDC) module at regular intervals. When the ECM fails to receive expected messages within a timeout window, it sets this fault code and disables stability features to prevent unpredictable behavior.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| CAN Bus Message Timeout | VDC module responds within 100-500ms | No response for >1 second or missing heartbeat frames |
| CAN Bus Signal Integrity | Valid checksums and frame IDs received | Corrupted or missing CAN messages detected |
Code U0122 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, U0122 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.