U019F

Lost Communication With Battery Sensor Control Module B

U019F is a generic OBD-II network diagnostic trouble code: Lost Communication With Battery Sensor Control Module B. 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
U019F
Group
Network
System
Network
Severity
Information only
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What U019F means

U019F is set when the controlling module -- commonly the BCM or power management controller -- ceases to receive serial data messages from a second Battery Sensor Control Module, designated B. Intelligent battery sensors integrate a current and temperature transducer on the battery negative cable and transmit state-of-charge and state-of-health data over a LIN or CAN bus to the power management module. Modern start-stop (ISG) systems, regenerative braking, and advanced charging strategies depend on this data to decide when the engine may be stopped and what generator target voltage to apply.

The 'B' designation indicates a secondary sensor, which may be present on vehicles with a dual-battery arrangement (e.g., a starter battery and a separate auxiliary battery for an AGM or EFB system) or on platforms where two battery management sensors are installed for redundancy. Loss of the B sensor typically degrades but does not eliminate power-management function; the system may fall back to a fixed-charge strategy and disable stop-start.

Physical inspection of the battery sensor itself and its LIN or CAN wiring are the first steps, as these sensors are mounted directly on the battery terminal where vibration, corrosion, and accidental disconnection are common. Confirm the sensor is the correct part number for the battery type installed, as fitting a replacement sensor without proper coding can also prevent communication.

Common causes

Most-frequently reported root causes when U019F is logged.

  • 1
    Loose, corroded, or improperly seated battery sensor B on the negative battery terminal.
  • 2
    Open or short in the LIN or CAN data wire between the BCM and battery sensor B.
  • 3
    Failed battery sensor B module (internal transducer or communication hardware).
  • 4
    Battery sensor B not coded or matched to the BCM after replacement.
  • 5
    Secondary battery (auxiliary) disconnected or removed, leaving sensor B without supply.
  • 6
    Poor battery negative ground connection at the chassis causing communication errors.
  • 7
    Water or corrosion at the sensor connector from battery acid or engine-bay moisture.

Symptoms drivers notice

MIL or battery/charging warning lamp illuminated.
Automatic start-stop system disabled or inoperative.
Generator charging voltage may default to a fixed value rather than a dynamic target.
Battery state-of-charge reading absent or frozen on the instrument cluster.

How to diagnose U019F

A typical diagnostic flow when this code is present.

  1. 1
    Record all DTCs; note any charging-system or start-stop related codes stored with U019F.
  2. 2
    Physically inspect battery sensor B at the battery negative terminal for tightness, corrosion, and physical damage.
  3. 3
    Verify the sensor's supply voltage and ground continuity.
  4. 4
    Use a scan tool to attempt communication with the battery sensor module and read live current and temperature data.
  5. 5
    Inspect the LIN or CAN wire from the sensor to the BCM for damage or corrosion.
  6. 6
    If the sensor was recently replaced, confirm it was coded to the BCM per the manufacturer's procedure.
  7. 7
    Replace battery sensor B if wiring and coding checks are satisfactory and communication cannot be established.

Related network codes

Frequently asked questions

What is the difference between U0198 and U019F?

U0198 refers to the primary (A) battery sensor module, while U019F refers to the secondary (B) battery sensor. Both codes indicate lost serial data communication, but with different sensor nodes.

Can I drive with U019F active?

Generally yes for short periods, but the power management system will operate in a degraded mode. Start-stop will be disabled and charging may not be optimised, which can shorten battery life over time.

Does replacing the battery require recoding the sensor?

On many modern vehicles, yes. The battery sensor must be adapted or coded to the BCM whenever a new battery is installed so that the power management system recalibrates its state-of-charge baseline.

Could a corroded battery terminal clamp cause U019F without the sensor itself being faulty?

Yes. The sensor is clamped to the battery terminal; if the terminal connection is loose or corroded, the sensor may lose its supply or ground reference, causing it to drop off the bus and setting U019F.

Disabling U019F in software

RaceTune can permanently disable U019F — 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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