What it means
A receiving module detected implausible data from body control module E. BCM-relayed signals (door/lock/lighting state, ignition, theft) fail plausibility checks and are rejected.
How it works
A receiving module checks messages from body control module E about body functions such as door locks, lighting, ignition state, or theft protection. U0446 sets when a message from BCM E fails the receiving module’s plausibility checks, so that module rejects it; the code alone does not prove BCM E is faulty.
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 record freeze-frame data and related communication codes to identify which module logged U0446 and what function was affected.
- Check whether the affected door, lock, lighting, ignition, or theft-protection function behaves incorrectly, and compare its reported status with what is physically happening.
- Inspect BCM E and gateway connectors, grounds, and network wiring for loose connections, corrosion, damage, or signs of recent repair.
- Use a scan tool to compare BCM E’s live data for the relevant body input with the receiving module’s interpretation of that message.
- If the code began after module replacement or programming, verify software compatibility and configuration for BCM E and the receiving module.
- Test the relevant network circuits and module power and grounds using the vehicle’s wiring information and manufacturer’s specifications before condemning a module.
Common fixes
- Repair a loose, corroded, or damaged BCM E connector or network wire.
- Repair a faulty input or connection causing BCM E to report an incorrect body-function state.
- Correct module configuration or software compatibility after replacement or programming.
- Repair a gateway routing or network fault if testing identifies one.
- Replace BCM E only if its inputs, power, grounds, network, and software check out and the invalid data persists.
Can I keep driving?
If only a convenience feature is affected and the vehicle otherwise operates normally, a short cautious drive may be possible. Avoid driving if the fault affects locks, lighting, ignition, theft protection, or another function needed for safe operation.
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.