U0619

Lost Communication With Steering Angle Sensor Module

U0619 is a generic OBD-II network diagnostic trouble code: Lost Communication With Steering Angle Sensor Module. It is logged by the engine control unit when the network monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
U0619
Group
Network
System
Network
Severity
Warning (MIL on, possible limp mode)
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What U0619 means

DTC U0619 is a network communication code set when the engine or aftertreatment control module loses valid serial communication with Reductant Level Sensor A over the vehicle data bus. This sensor reports the level of diesel exhaust fluid (DEF/AdBlue) in the reductant tank, information the SCR system uses to manage dosing and to warn the driver of a low reductant condition.

The fault is a lost-communication condition rather than a low-fluid reading. It is triggered when the expected data frames from the reductant level sensor node are missing or corrupted for a calibrated number of message cycles. Because the sensor is tank-mounted and often part of a combined reductant sender or heater assembly, root causes are usually electrical: open or shorted bus wiring, loss of power or ground, connector corrosion, or a failed sensor module.

When U0619 is active, the SCR system cannot confirm reductant level. Emissions regulations require the vehicle to respond to unresolved SCR faults with escalating warnings, reduced power, and eventually a speed limit or no-restart inducement. Diagnosis should verify the sensor is present on the network and confirm its power and ground before replacement, since wiring and connector faults near the tank are common triggers.

Common causes

Most-frequently reported root causes when U0619 is logged.

  • 1
    Open, short, or high-resistance fault in the bus wiring to Reductant Level Sensor A.
  • 2
    Failed reductant level sensor or its combined sender/heater interface module.
  • 3
    Loss of power or ground supply to the reductant level sensor circuit.
  • 4
    Corroded, loose, or damaged connector at the reductant tank sensor.
  • 5
    Chafed or damaged wiring harness routed to the reductant tank.
  • 6
    Blown fuse supplying the sensor or its host module.
  • 7
    Contamination or crystallized DEF affecting the sensor connector or module.

Symptoms drivers notice

Check engine light and SCR/DEF warning message illuminated.
Reductant (DEF) level reading unavailable, frozen, or implausible on the dashboard.
Escalating low-DEF or emissions-system warnings.
Reduced engine power, speed limiting, or a no-restart inducement over time.
Possible additional SCR or communication DTCs stored alongside U0619.

How to diagnose U0619

A typical diagnostic flow when this code is present.

  1. 1
    Retrieve all stored DTCs from every module and note any related SCR or network codes.
  2. 2
    Check live data to confirm whether the reductant level sensor is reporting on the bus or reads as missing.
  3. 3
    Inspect the sensor connector and harness at the reductant tank for corrosion, DEF crystals, or damage.
  4. 4
    Verify power and ground at the sensor connector with a multimeter and the wiring diagram.
  5. 5
    Measure bus integrity (approximately 60 ohms across CAN-H and CAN-L) to rule out wiring or termination faults.
  6. 6
    Attempt communication with the sensor or host module; if absent, confirm supply before condemning it.
  7. 7
    Replace the reductant level sensor only after wiring, power, and ground have been confirmed good.

Related network codes

Frequently asked questions

What does U0619 actually monitor?

It is a lost-communication code for Reductant Level Sensor A, which reports the diesel exhaust fluid (DEF/AdBlue) level to the SCR system.

Why does U0619 matter for driveability?

Because emissions rules require the vehicle to respond to unresolved SCR faults with warnings and eventually power or speed limiting until repaired.

Does U0619 always mean the sensor is faulty?

No. Wiring, connector, power, and ground faults near the reductant tank are common, so verify those before replacing the sensor.

Is U0619 a steering angle sensor code?

No. Lost communication with the steering angle sensor module is code U0126; U0619 refers to the reductant level sensor.

Disabling U0619 in software

RaceTune can permanently disable U0619 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

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