What this code means
U0104 may mean the gauge control module has lost communication with the driving support system control unit.
What the vehicle may do
- The vehicle may show driver-assist warnings.
- Some driving support features may be unavailable.
- The code can be stored even when the vehicle otherwise seems to operate normally.
Possible fault areas
- Possible CAN communication or gateway-related fault area.
- Possible millimeter wave radar startup, power, or ground issue.
- Possible wiring or connector concern in the communication or radar circuits.
- Possible issue with expected data not reaching the gauge control module.
Diagnostic path
Code overview
On this 2020 to 2025 Honda CR-V Hybrid, U0104 means the gauge control module lost communication with the driving support system control unit. In plain terms, the cluster is expecting data from the driving support side of the vehicle and is not seeing it correctly. The vehicle may show driver-assist warnings, may disable some support features, or may store the code without an obvious drivability complaint. Broadly, think about possible communication network issues, a module that did not wake up normally, connector or wiring problems, and power or ground problems feeding the radar side of the system.
Check the radar power and ground first
Before getting deep into network diagnosis, check the power and ground circuit for the millimeter wave radar first. This code may set if that radar does not start normally, and a power or ground fault there can make the gauge control module lose the data it expects to receive.
Start the diagnostic path cleanly
Before chasing the code, start with the basic system checks and follow a structured diagnostic approach. If other codes are present, do not treat U0104 in isolation. Use the multiple-code B-CAN diagnostic routine first so the communication fault is handled in the right order.
Follow the communication fault path
For U0104, the target path is the F-CAN lost communication diagnosis for the CAN bus that connects through the CAN gateway. Keep the diagnosis focused on why the gauge control module is not receiving the specified data from the millimeter wave radar, instead of jumping straight to module replacement.
Power the vehicle for testing
When you are ready to run the checks in that path, turn the vehicle to the ON mode. From there, follow the communication diagnosis in order. If the path becomes unclear, pause, recheck the earlier diagnostic path, and avoid guessing.
Verification and takeaway
After the fault path is completed, verify the repair and confirm the code stays gone. The key point with U0104 is to prove the radar side can power up and communicate, then prove the gauge control module is receiving the data it expects. For more diagnostic training, visit stepdiagnostics.com.
Final check
U0104 is best approached as a communication diagnosis: confirm the radar side can wake up and has proper support circuits, then follow the F-CAN lost communication path.
For more guided automotive diagnostics, visit STEP Diagnostics.
