Code
U061D
Generic
U — Network/User
Lost Communication With Reductant Temperature Sensor B
Views:
UK: 20
EN: 29
RU: 19
AI status
Completed
Completed
100%
Causes
- Open or short in sensor B signal, supply, or ground circuit
- Corroded/loose connector at the reductant temperature sensor B
- Defective reductant temperature sensor B (thermistor or sender)
- Faulty wiring harness (chafing, water intrusion, pinched)
- Loss of sensor power/ground (fuse, relay, module output)
- CAN/LIN network fault or module not reporting sensor data
Symptoms
- DTC U061D stored or lamp/warning related to SCR/reductant system
- Reduced or disabled reductant dosing (engine derate possible on some vehicles)
- Unavailable reductant temperature B data in scan tool
- Intermittent or no change in measured temperature for sensor B
- Other network communication DTCs present (related modules)
What to check
- Read and record all related DTCs and freeze frame data with a scan tool
- Visually inspect the sensor B connector and wiring for damage, corrosion, or water
- Backprobe sensor connector while monitoring live data — check for presence of reference voltage and ground
- Check harness continuity and resistance between sensor connector and control module pins
- Verify CAN/LIN bus health: measure bus idle voltages and termination resistance, check for related network codes
- Compare readings from Reductant Temperature Sensor A and B (if present) for plausibility
Signal parameters
- Sensor type: commonly an NTC thermistor (resistance varies with temperature) or voltage-output temperature sender
- Expected output: resistance or voltage that changes smoothly with temperature (not open/short). Typical range covers ambient to high reductant temperatures (-40°C to +125°C) but values are vehicle-specific
- Reference supply: often low-voltage reference (5V) or ground reference — verify with OEM data
- Network: sensor data may be reported on a CAN or LIN message by a module; confirm presence of frames and that values update with temperature change
- Electrical checks: continuity to module, no short to battery or ground, no excessive resistance in circuit
Diagnostic algorithm
- Retrieve all codes and live data. Note whether only U061D is present or other network/sensor codes exist.
- Perform visual inspection of sensor B connector and wiring. Look for bent pins, corrosion, water, or crushed wiring.
- With ignition on (and engine off unless OEM directs otherwise), backprobe the sensor connector: verify reference voltage/pull-up, signal line behavior, and good ground. Record voltages.
- If the sensor is a thermistor, measure resistance across sensor terminals at known temperatures (ambient and warmed) and confirm it changes. If voltage-output type, verify signal varies with temperature.
- Check harness continuity between the sensor connector and the control module pin. Repair any opens or high-resistance connections.
- Verify CAN/LIN bus operation: check idle voltages, termination (approx. 60 ohms across CAN_H and CAN_L), and use a scope or diagnostic tool to confirm messages containing reductant temperature B are present and updating.
- Wiggle the wiring and connectors while watching live data to identify intermittent faults. Clean and reseal connectors if corrosion present.
- If wiring and network are good but no proper signal, substitute a known-good sensor or connector assembly if available to confirm sensor failure before replacement.
- After repairs, clear codes, perform a relearn or module initialization if required by OEM, then road test and re-scan to confirm U061D does not return.
- If fault persists after sensor and wiring verification, consider module/software issues and consult OEM service information for module testing or reprogramming.
Likely causes
- Connector corrosion or water ingress at the DEF temperature sensor
- Broken/shorted wire in harness between sensor B and control module
- Sensor B internal failure (open/short thermistor or failed electronics)
- Loss of reference supply or ground to sensor circuit
- CAN bus message from sensor's module not present or corrupted
Fault status
Status
Lost Communication With Reductant Temperature Sensor B — the control module is not receiving valid sensor data or communication from the reductant temperature sensor designated B. Check wiring, connector, sensor, power/ground and the vehicle network.
Repair difficulty: Medium
Diagnostic time: 1.0 - 2.5 hours
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