What it means
The vehicle bus reports loss of communication with smart engine coolant bypass valve B. Bypass switching for thermal management cannot be commanded.
At a glance
- Usually lights the warning light of the system that lost communication
How it works
Smart engine coolant bypass valve B helps direct coolant for thermal management and reports its status over the vehicle communication bus. U0616 sets when the control module stops receiving messages from valve B, so that valve's bypass switching cannot be reliably commanded or confirmed.
Common causes
Most likely first.
- Bus wiring open or shorted
- Module without power or ground
- Module failed
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
- Save freeze-frame data and scan all modules for communication faults to see whether the loss is isolated to valve B.
- Check live coolant-temperature data and valve B status for a missing response or unavailable position information.
- Inspect valve B's connector and bus wiring for looseness, corrosion, coolant intrusion, chafing, or heat damage.
- Verify power and ground at the valve B module using the manufacturer's wiring information.
- Test valve B's communication circuit for opens or shorts using the manufacturer's procedure and repair any fault found.
- If wiring and supply are sound, confirm valve B's bus communication before replacing its module.
Common fixes
- Reconnect and secure the engine coolant bypass valve B connector.
- Clean corrosion or repair damaged terminals at valve B's connector.
- Repair an open, short, or damaged section of valve B's communication wiring.
- Restore power or ground to the valve B module.
- Replace the valve B module if it fails testing after its circuit is verified.
Can I keep driving?
If the engine temperature is normal and there are no overheating warnings, limit driving and monitor the temperature because valve B may not switch coolant flow as intended. Stop safely if the temperature rises or a warning appears.
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.