Lost Communication With Suspension Control Module B
Your vehicle's main computer has lost the ability to talk to the suspension control module, like a walkie-talkie losing its signal. This communication breakdown prevents proper suspension adjustments and safety features from functioning.
The ECM constantly sends and receives CAN bus signals to the Suspension Control Module B to verify active communication. It monitors for response timeouts and signal integrity on the dedicated network line. If no acknowledgment is received within the expected window or signal quality degrades, the fault is triggered.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| CAN Bus Message Response Time | < 100 milliseconds | > 500 milliseconds or no response |
| Signal Quality/Checksum Validation | Valid checksum, consistent frames | Invalid checksum or missing frames for 2+ cycles |
Code U0139 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, U0139 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.