Lost Communication With Body Control Module C
Your engine's main computer lost contact with the body control module, which handles functions like lights, windows, and locks. It's like two walkie-talkies that can't hear each other anymore.
The ECM monitors CAN bus voltage and message timing from the BCM. Communication is expected to occur within set intervals; if no valid messages are received within the timeout threshold, a fault is triggered. The ECM detects loss of signal, voltage drops, or corrupted data frames.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| CAN Bus Voltage | 2.5-3.5V nominal | <0.5V or >5.5V for >500ms |
| BCM Message Timeout | Message received every 10-100ms | No valid message for >1000ms |
Code U0143 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, U0143 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.