What it means
The Body Control Module is present on the data bus but the values it reports are implausible — out of range, frozen, or failing the checksum or rolling-count check. The receiving modules reject the data. Body functions such as lighting or central locking may misbehave. Causes include a faulty sensor feeding the module, internal computation errors, a software or calibration mismatch after a repair, or bus interference corrupting the frames.
At a glance
- Usually lights the warning light of the system that lost communication
How it works
The Body Control Module (BCM) manages body functions such as lighting and central locking and shares status data with other modules. U0422 sets when a receiving module rejects BCM data as implausible, which may result from faulty BCM inputs, corrupted network messages, or a routing or configuration problem.
Common causes
Most likely first.
- BCM internal fault
- CAN corruption causing checksum errors
- 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 details to identify which modules report invalid BCM data and whether other CAN faults are present.
- Check which body functions are affected, such as lighting or central locking, and note whether several unrelated functions failed at the same time.
- Inspect BCM connectors, grounds, and nearby network wiring for poor connections, corrosion, water intrusion, or damage.
- Check BCM power and ground circuits to the manufacturer's specification and inspect relevant input data for frozen or implausible values.
- Test CAN communication and gateway message routing using the vehicle's service information, then check for software or configuration mismatches after recent repairs.
- Replace or reprogram the BCM only after its inputs, power, grounds, network wiring, and configuration have been checked.
Common fixes
- Repair a poor BCM connector, ground, or damaged network connection.
- Repair a faulty sensor or input circuit feeding implausible data to the BCM.
- Correct a gateway routing or configuration issue.
- Apply the appropriate BCM software or calibration update.
- Replace the BCM if its inputs, supply, and network connections test correctly but it continues to send invalid data.
Can I keep driving?
If lighting, locking, or other body functions are unreliable, check that essential lights work before driving and avoid driving if visibility or vehicle security is compromised. Multiple warning lights can reflect the same communication fault, so diagnose the BCM network promptly.
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.