U061D: Lost Communication With Reductant Temperature Sensor B

What it means

The vehicle bus reports loss of communication with smart reductant (DEF/AdBlue) temperature sensor B. Heater control and freeze protection lose their primary feedback.

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

Smart reductant temperature sensor B sends DEF/AdBlue temperature data over the vehicle network. U061D sets when expected messages from sensor B stop arriving, so heater control and freeze protection lose this sensor's feedback even if sensor A still reports normally.

Common causes

Most likely first.

1. Bus wiring open or shorted
2. Module without power or ground
3. 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

1. Scan all modules for communication codes and record freeze-frame data to check whether sensor B's fault coincided with other network or voltage faults.
2. Check live data for reductant temperature sensor B and compare its status with sensor A and the actual reductant temperature.
3. Inspect sensor B's connector and its bus wiring for corrosion, loose pins, heat damage, or an open or short.
4. Check the sensor module's power and ground using the manufacturer's wiring information.
5. Test the network wiring to sensor B for continuity and shorts using the manufacturer's procedure.
6. If the wiring and supply are sound, verify whether sensor B is transmitting before replacing its module.

Common fixes

• Repair damaged wiring or connector terminals at reductant temperature sensor B.
• Restore the sensor module's power or ground connection.
• Repair an open or short in the network circuit serving sensor B.
• Replace sensor B's module if it has proper power, ground, and network wiring but does not communicate.

Can I keep driving?

Avoid relying on normal DEF/AdBlue heating or freeze protection while this fault is active, particularly in freezing conditions. Have it checked promptly if a reductant warning or emissions restriction appears.