Lost Communication With Automatic Lighting Control Module
Your car's main computer can't talk to the automatic headlight control module, like a walkie-talkie with a dead battery. This breaks communication on the CAN bus network that controls automatic lighting features.
The ECM monitors CAN bus communication frames from the Automatic Lighting Control Module at regular intervals. When expected messages don't arrive within the timeout window, a communication fault is registered. The system expects valid heartbeat signals and data packets within 100-500ms depending on vehicle architecture.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| CAN Message Timeout | Message received every 100-500ms | No message received for >500ms |
| Bus Voltage | 12-14.5V on CAN lines | <10V or >15V indicates wiring issue |
Code U0180 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, U0180 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.