Faulty reductant level sensor B itself, including internal failure or contamination; Damaged or corroded wiring or connector at the sensor or along the harness; Open or short circuit in the communication bus wiring between the sensor and the control module; Failed reductant control module or engine control module not communicating properly; Low or contaminated DEF fluid causing the sensor to send implausible readings; Software glitch or need for module reprogramming; Poor ground connection for the sensor or control module

DTC codes / U06xx · Network communication / U061A

U061ALost Communication With Reductant Level Sensor B

Q: What does code U061A mean?

Lost Communication With Reductant Level Sensor B. U061A is a generic communication fault indicating that a control module on the vehicle's network has lost contact with the reductant level sensor B, which is part of the diesel exhaust fluid (DEF) system on diesel vehicles. The module that monitors this sensor, typically the engine control module or a dedicated reductant control module, has stopped receiving valid data from the sensor over the serial data bus for a calibrated period.

U061A is a generic communication fault indicating that a control module on the vehicle's network has lost contact with the reductant level sensor B, which is part of the diesel exhaust fluid (DEF) system on diesel vehicles. The module that monitors this sensor, typically the engine control module or a dedicated reductant control module, has stopped receiving valid data from the sensor over the serial data bus for a calibrated period.

SystemNetwork

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaNetwork communication

Symptoms you may notice

Illumination of the malfunction indicator lamp (MIL) on the dashboard
A message on the driver information center indicating a DEF system fault or low DEF level warning
The vehicle may enter limp mode or limit engine power after a certain number of key cycles
No noticeable drivability symptoms besides the warning light in many cases
In some vehicles, the remote start or other features may be disabled
The DEF level gauge may read incorrectly or stay at a fixed value

Common causes, most likely first

Faulty reductant level sensor B itself, including internal failure or contamination
Damaged or corroded wiring or connector at the sensor or along the harness
Open or short circuit in the communication bus wiring between the sensor and the control module
Failed reductant control module or engine control module not communicating properly
Low or contaminated DEF fluid causing the sensor to send implausible readings
Software glitch or need for module reprogramming
Poor ground connection for the sensor or control module

How to diagnose and fix it

Verify the DEF level and condition; top off or replace fluid if contaminated
Inspect the sensor connector and wiring for damage, corrosion, or loose pins
Check for continuity and short circuits in the communication bus wiring between the sensor and the control module
Perform a visual inspection of the sensor for physical damage or debris
Use a scan tool to check for other codes and to perform a bidirectional test of the sensor if supported
If wiring and fluid are good, test the sensor with a multimeter according to manufacturer specifications
Replace the reductant level sensor B if it fails testing, then clear codes and verify communication

Reductant sensor communication faults often misdiagnosed

A low DEF level or contaminated fluid can cause the sensor to send erratic signals that the module interprets as a communication loss, so always check fluid quality first.
The code may be set by a completely dead battery or low voltage condition that temporarily disrupted module communication, so check battery health and clear the code to see if it returns.
On many vehicles, the reductant level sensor is part of a combined sensor assembly that includes temperature and quality sensors, and a failure in any of these can trigger U061A.
Corrosion at the sensor connector is a common cause that is often overlooked because the connector may look fine from the outside; disconnecting and inspecting the pins is essential.
After replacing the sensor, some vehicles require a relearn or adaptation procedure using a scan tool to restore proper communication and avoid a repeat code.

Can I keep driving with U061A?

You can usually continue driving for a short period, but the vehicle may eventually limit speed or power to protect the emissions system, so schedule diagnosis and repair promptly. Avoid long trips or heavy loads until the fault is resolved.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.