Lost Communication With Fuel Cell Control Module
Your main computer lost its connection to the fuel cell control module, like a radio station losing its signal. The vehicle can't communicate with the fuel cell system to manage power generation.
The main ECU monitors CAN bus communication frames from the fuel cell control module at regular intervals. When expected messages fail to arrive within a timeout window, the ECU logs this U0119 fault. The system relies on continuous handshake signals to verify the fuel cell module is present and functional.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| CAN Bus Message Timeout | Messages received every 10-100ms | No messages received for >500ms |
| Fuel Cell Module Response | Module acknowledged and responding | No acknowledge signal detected |
Code U0119 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, U0119 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.