What it means
A module reports a software version mismatch with brake system control module B — typically after replacing one of the modules without programming the new unit to match the rest of the network.
At a glance
- Usually lights the warning light of the system that lost communication
- The engine or gearbox may go into limp mode
How it works
A controller checks software and configuration compatibility with brake system control module B over the vehicle network. U031C sets when the reported version or configuration for that specific brake module does not match what the detecting controller expects, often after a module replacement or incorrect programming.
Common causes
Most likely first.
- Module replaced without programming
- Wrong part number for the vehicle
- 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 or event data before clearing anything, noting which controller logged U031C and any brake or network codes stored with it.
- Check whether brake system control module B or another network module was recently replaced, updated, or configured, since the timing can point to an unprogrammed change.
- Inspect the brake module B connectors and nearby harness for loose plugs, corrosion, water ingress, or damage that could disrupt its network messages.
- Use a capable scan tool to compare the reported identity, software version, and configuration of brake system control module B with the vehicle's required information.
- Check gateway routing and network communication records for faults affecting messages to or from brake system control module B.
- Have the correct module software and vehicle configuration restored using the manufacturer's programming procedure, then rescan to confirm U031C does not return.
Common fixes
- Correct a loose or corroded connector at brake system control module B.
- Program or configure the replacement brake system control module B to the vehicle.
- Install the correct brake module for the vehicle if the fitted unit is incompatible.
- Correct gateway configuration or routing if it is misdirecting brake module B network messages.
Can I keep driving?
Because this fault concerns the brake control system, do not assume normal braking assistance or stability functions are available if warnings are on or braking behavior changes. Avoid unnecessary driving and arrange prompt diagnosis; reduced or unavailable brake functions can affect control and stopping.
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.