What it means
A receiving module detected implausible data from body control module B. BCM-relayed signals (door/lock/lighting state, ignition, theft) fail plausibility checks and are rejected.
How it works
Body Control Module B shares body-related status information with other modules over the vehicle network. U0443 is set when a receiving module judges a message from BCM B—such as a reported door, lighting, ignition, or security state—to be implausible and rejects it; the exact affected function depends on the vehicle.
Common causes
Most likely first.
- Module internal fault or sensor input drift
- Software version mismatch after replacement
- Gateway module routing CAN messages incorrectly
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
How to diagnose it
- Scan all modules and save freeze-frame and communication codes to identify which module rejected BCM B data and what functions reported a problem.
- Check live body data from BCM B, including relevant door, lighting, ignition, or security states, for values that disagree with the actual vehicle condition.
- Inspect BCM B connectors, grounds, power connections, and network wiring for damage, loose terminals, or corrosion.
- Check for gateway faults and related communication codes that could affect messages from BCM B.
- If BCM B or another module was replaced, verify software compatibility and configuration, then test the affected body functions using the manufacturer's procedure.
Common fixes
- Repair loose, corroded, or damaged BCM B wiring and connectors.
- Correct a gateway or network fault confirmed to affect BCM B messages.
- Update or configure replacement BCM B software for the vehicle.
- Repair a confirmed faulty input or internal fault in BCM B.
- Replace BCM B only after testing rules out wiring, network, and configuration issues.
Can I keep driving?
The code may affect body functions such as locks, lighting, ignition status, or security, depending on the vehicle. Check that lights and doors operate correctly before driving, and do not drive if a visibility or vehicle-security warning leaves the vehicle unsafe.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.