Lost Communication With Television
Your vehicle's main computer has lost communication with the television/display module, like two phones unable to reach each other. This prevents information from being sent to your dashboard screen.
The ECM monitors bus communication signals (CAN/LIN) to the instrument cluster TV module at regular intervals. If no acknowledgment is received within the expected timeout window, the fault is triggered.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| CAN Bus Message Timeout | 100-500ms response time | No response >2 seconds |
| Bus Voltage Level | 5V nominal signal | <2V or >6V sustained |
Code U0191 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, U0191 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.