Lost Communication With Cruise Control Module
Your car's main computer lost its connection to the cruise control module, like a phone losing signal to a connected device. The cruise control system can't communicate with the engine computer to maintain speed.
The ECM monitors CAN bus communication signals from the cruise control module at regular intervals. When the expected message fails to arrive within the timeout threshold, the ECM logs a communication fault. The module checks for valid data packets and electrical integrity on the network.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| CAN Bus Message Timeout | Message received every 100-500ms | No message received for >1000ms |
| Signal Voltage | 0-5V with valid CAN protocol | Open circuit or short circuit detected |
Code U0104 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, U0104 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.