What it means
The vehicle bus reports loss of communication with smart reductant (DEF/AdBlue) level sensor B. Tank-level monitoring switches to a substitute model; refill warnings may be incorrect.
At a glance
- Usually lights the warning light of the system that lost communication
- Affects emissions; the car can fail an emissions test
How it works
Reductant level sensor B monitors DEF or AdBlue tank level and reports it to vehicle modules over the communication bus. U061A sets when messages from sensor B are lost, so the control system may estimate the tank level and display inaccurate refill warnings.
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 determine whether sensor B is the only device affected.
- Check live data for reductant level sensor B and compare it with the actual tank level and any available sensor A reading.
- Inspect sensor B's connector and bus wiring near the tank for loose pins, corrosion, fluid contamination, or damaged insulation.
- Verify power and ground at the sensor B module using the manufacturer's wiring information.
- Test the sensor B communication circuit for opens or shorts using the manufacturer's procedure and repair any fault found.
- If power, ground, and wiring pass, verify sensor B's bus messages before replacing the module.
Common fixes
- Reconnect and secure the reductant level sensor B connector.
- Clean corrosion or repair damaged terminals at sensor B's connector.
- Repair an open, short, or damaged section of sensor B's communication wiring.
- Restore power or ground to the sensor B module.
- Replace reductant level sensor B if it fails testing after the circuit is verified.
Can I keep driving?
If the vehicle runs normally, limited driving is generally possible, but check the actual DEF or AdBlue level and arrange diagnosis before relying on the dashboard warning. A low tank may trigger emissions warnings or operating restrictions.
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.