Lost Communication With Active Roll Control Module
Your vehicle's main computer lost the radio signal to the active roll control module, like a walkie-talkie that stopped communicating. This safety system can't help stabilize the car during sharp turns until the connection is restored.
The ECM continuously polls the active roll control module via CAN bus to confirm communication status and receive suspension response data. If no acknowledge signal arrives within the expected timeout window, the fault is triggered. The module controls anti-roll bars to counteract body lean.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| CAN Bus Response Time | < 100 milliseconds | No response for > 500 milliseconds |
| Module Status Signal | Active/Ready state | No signal or timeout detected |
Code U0133 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, U0133 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.