U061B

Code

Generic U — Network/User

Lost Communication With Reductant Level Sensor C

Brand: Generic

Type: U — Network/User

Views: UK: 28 EN: 36 RU: 27

AI status

Completed

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Page language: EN

Causes

Open or short in sensor wiring (power, ground or data/CAN)
Corroded, damaged or disconnected connector at the reductant level sensor
Failed reductant level sensor (internal electronics or harness pigtail)
Faulty CAN bus or local network wiring (high resistance, short to battery/ground)
Failed ECU/module that reads the sensor or processes the message
Intermittent supply voltage or poor ground at the sensor

Symptoms

MIL (malfunction indicator lamp) or warning message about reductant/DEF system
Incorrect or unavailable DEF level gauge reading (blank, erratic, or frozen)
Possible reduced emissions system functionality or limp-home behavior on some vehicles
Stored network/communication DTCs in related modules

What to check

Read all related modules with a capable scan tool; capture freeze frame and live data for DEF level sensor C
Inspect connector at reductant tank level sensor for corrosion, moisture, bent pins or loose terminals
Visually inspect harness from sensor to junctions/modules for chafing, breaks or repairs
Confirm vehicle battery voltage is within specification and check for poor grounds near DEF tank/module
Check for other network errors on CAN bus (multiple modules reporting COMM faults)
Use DTC history to determine if fault is permanent or intermittent

Signal parameters

Sensor typically uses 5 V supply and ground; verify reference and ground presence at sensor connector
Sensor analog output (if used) usually varies between ~0.1–4.9 V depending on level; absent or stuck voltage indicates fault
If sensor is a CAN device, expect periodic CAN messages for that sensor (message rate varies by manufacturer, often 1–10 Hz); no messages = lost communication
Typical fault thresholds: no message timeout or invalid message CRC triggers U061B; short to ground or Vbatt will distort expected voltages

Diagnostic algorithm

Connect a factory-level or advanced scan tool. Read U061B and any related DTCs in the emission/engine and body modules. Note freeze-frame and current data.
Attempt to read live reductant level C data. If no data, confirm whether other reductant sensors (A/B) or related modules are visible on the network.
Perform a visual inspection of the sensor connector and harness at the DEF tank. Repair any obvious damage, clean and reseal corroded connectors.
With ignition ON, measure supply voltage and ground at the sensor connector. Compare to vehicle specification (typically ~5 V reference and chassis ground).
For analog sensors: probe sensor output while moving level or actuating float to see if voltage changes. For CAN sensors: use an oscilloscope or CAN bus analyzer to verify message presence and signal integrity on bus wires.
If wiring and power/ground are good but no data, unplugging/replugging the connector can verify intermittent connectivity (observe DTC and live data changes).
Backprobe and check continuity between sensor connector and the receiving module. Check for shorts to battery or ground. Repair wiring as required.
If wiring, power and CAN are confirmed good, consider reflashing or cycling power on the receiving module per OEM procedures. Check for available technical service bulletins.
Replace the reductant level sensor C only after confirming the wiring and bus are good and the sensor fails functional tests.
Clear codes and road/test to confirm the repair. Monitor network for recurrence and document intermittent conditions if present.

Likely causes

Corroded or water-intruded connector at the DEF tank sensor
Broken or pinched harness between the sensor and controller
Sensor internal electronics failed (no transmitter on bus)
CAN bus short or excessive resistance on branch to sensor

Fault status

⚠️ Status

Lost Communication With Reductant Level Sensor C — controller not receiving valid messages or expected signal from the reductant level sensor C (communication timeout/invalid data).

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.5 hours