U0619

Code

Generic U — Network/User

Lost Communication With Reductant Level Sensor A

Brand: Generic

Type: U — Network/User

Views: UK: 20 EN: 44 RU: 22

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Open or shorted wiring between sensor and control module
Corroded, loose or damaged connector at sensor or harness
Failed reductant level sensor (float, ultrasonic or electronic)
Loss of sensor power or ground (blown fuse, poor ground)
CAN/communication bus fault or module bus-off condition
Control module (ECM/PCM or DEF module) software or internal failure

Symptoms

Malfunction Indicator Lamp (MIL) or DEF system warning message
Incorrect or no displayed DEF level on dash
Reduced engine power or restricted performance in some vehicles
SCR/DEF dosing disabled or limited regen events
DTCs logged for reductant system and/or communications

What to check

Read stored and pending codes, freeze frame and relevant live data with a scan tool
Visually inspect DEF tank sensor, harness, and connectors for corrosion, loose pins, contamination, or damage
Check fuses and relays related to DEF system and instrument cluster/ECM power circuits
Verify sensor supply voltage (usually 5 V reference) and good ground at the connector
Measure sensor output while changing tank level (or with sensor actuator) to confirm varying signal
Check CAN/communication bus voltage levels and for other modules reporting communication errors

Signal parameters

Sensor supply/reference: typically ~5.0 V (±0.5 V) from control module
Sensor signal: generic level sensors produce a variable 0–5 V signal or a variable resistance proportional to level
Ground continuity:
CAN bus idle: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (differential ~0 V idle; active edges ±2 V) — verify with proper tool
Open-circuit signal: sensor line may read battery or floating voltage if open; resistance to ground may be high or infinite
Typical float sensor resistance: varies by design — check OEM spec before replacing

Diagnostic algorithm

Connect a capable scan tool. Retrieve U0619 and any related codes (other U-codes, DEF/level sensor codes). Record freeze frame and live data for reductant level.
Visually inspect DEF tank area, sensor connector and wiring for contamination, corrosion, pin damage, chafing, breaks, or evidence of fluid intrusion.
With ignition on (engine off), backprobe the sensor connector. Verify reference voltage (≈5 V), ground continuity, and signal voltage. Note readings.
If no reference or ground, trace wiring back to fuse/relay and control module; check and replace any blown fuse, repair poor ground, and re-test.
If reference and ground are present but no or static signal, operate or change tank level (fill or move float, or simulate level if safe) while monitoring signal voltage. If signal does not change, suspect sensor or wiring to sensor.
Perform continuity check between sensor connector and control module connector for power, ground, and signal lines. Repair any opens/shorts found.

Likely causes

Corroded/loose connector at reductant level sensor
Damaged wiring harness (abrasion, chafe, pinched or rodent damage)
Failed reductant level sensor
Blown fuse or poor ground for sensor power
CAN bus fault or module communication error

Fault status

⚠️ Status

Lost communication with reductant level sensor A — control module not receiving valid level data from the DEF/AdBlue tank sensor. This may disable proper SCR/DEF operation and trigger emissions warnings.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours