What it means
A control module received data from Brake System Control Module B that it judged invalid or implausible. This code does not identify which data was rejected or which brake-related functions are affected.
At a glance
- Usually lights the warning light of the system that lost communication
How it works
Brake System Control Module B is a distinct brake controller whose status is shared with other vehicle systems. U0419 sets when a receiving module rejects data from this specific B module as invalid or implausible; the code alone does not show which reported brake function or input is at fault.
Common causes
Most likely first.
- Fault or implausible input at Brake System Control Module B
- Damaged or loose network wiring or connector
- Module power, ground, or programming issue
Symptoms
- Brake-system warning message
- Brake-related electronic functions may be limited
- Other communication codes
How to diagnose it
- Scan all modules and preserve freeze-frame data; identify the module storing U0419 and check specifically for codes reported by Brake System Control Module B.
- Review live data attributed to Module B, such as brake status and available pressure or pedal signals, and look for missing or contradictory readings.
- Inspect Module B's connector and accessible network wiring for damage, corrosion, moisture, or a loose fit, taking care not to assume the primary brake module is the sender.
- Check Module B's own input and communication codes and confirm basic brake operation before any road test.
- If the data and visual checks do not isolate a fault, test Module B power, ground, and network circuits to the manufacturer's specification and check for applicable programming.
Common fixes
- Secure or repair Module B's connector or damaged network wiring.
- Repair the input sensor or circuit identified by Module B's own codes and live data.
- Restore Module B's power or ground connection if testing finds a fault.
- Update or replace Brake System Control Module B only after its inputs and circuits are verified.
Can I keep driving?
Brake-related electronic assistance may be limited, so stop driving if a brake warning appears or pedal feel or stopping changes; arrange recovery if basic braking is affected. If braking remains normal, proceed cautiously to a safe location and have the code diagnosed.
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.