What it means
A control module has stopped receiving expected network messages from coolant bypass valve actuator B. The effect on coolant routing depends on the vehicle's system design.
At a glance
- Usually lights the warning light of the system that lost communication
How it works
Coolant bypass valve actuator B helps route coolant through a selected cooling path. A control module monitors messages from actuator B or its controller over the vehicle network. U063C sets when those expected messages are lost, which can leave the module unable to confirm coolant routing at valve B.
Common causes
Most likely first.
- Bus wiring open or shorted
- Module without power or ground
- Module failed
Symptoms
- Warning light or message related to the affected system
- Cooling or temperature control may be affected
How to diagnose it
- Scan all modules and review freeze-frame data for communication faults associated with coolant bypass valve actuator B.
- Check live data for actuator B status and commanded position, if available, to confirm whether its reported information is missing or frozen.
- Inspect actuator B’s connector and network wiring for looseness, corrosion, chafing, or coolant intrusion.
- Check power and ground at actuator B or its controller against the manufacturer’s specification.
- Test the network circuit for opens or shorts, then evaluate the actuator B reporting module if the wiring and supplies pass.
Common fixes
- Reconnect or clean and secure actuator B’s network connector.
- Repair an open, short, or damaged network wire to actuator B.
- Restore power or ground to the actuator or controller.
- Replace the failed actuator B reporting module if circuit checks verify an internal fault.
Can I keep driving?
If a coolant or temperature warning appears, avoid heavy loads and extended driving because coolant routing may be compromised and overheating can result. Stop if the temperature rises or the vehicle warns of a cooling problem.
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.