U0D97

Lost Communication With High Voltage Battery Charger Control Module

U0D97 is a generic OBD-II network diagnostic trouble code: Lost Communication With High Voltage Battery Charger Control 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
U0D97
Group
Network
System
Network
Severity
Warning (MIL on, possible limp mode)
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What U0D97 means

U0D97 is stored when the vehicle control system loses CAN bus communication with the high-voltage battery charger control module, which governs the on-board AC charging process for the high-voltage traction battery on plug-in hybrid and battery electric vehicles. This module manages AC-to-DC conversion, charging current and voltage regulation, and communicates charging state to the vehicle management system.

Loss of communication with this module prevents the vehicle from initiating or monitoring AC charging sessions. Depending on the platform, the fault may also restrict vehicle operation as a precaution if the high-voltage system safety status cannot be confirmed. Common causes include a loss of 12V supply voltage to the charger module, a CAN bus wiring fault in the charging system harness, or a failed charger module.

Diagnosis must follow high-voltage safety precautions. The low-voltage supply and bus wiring should be confirmed before suspecting a failed charger module, as the charger is a significant and expensive component. Co-set charging system codes should be reviewed alongside U0D97 to build a complete picture of the system state before any components are replaced.

Common causes

Most-frequently reported root causes when U0D97 is logged.

  • 1
    Loss of 12V control power or ground to the on-board charger control module.
  • 2
    Open or shorted CAN bus wiring between the charger module and the vehicle network.
  • 3
    Failed on-board charger control module no longer responding on the CAN bus.
  • 4
    Corroded or damaged connector at the charger module, often in the engine bay or charging port area.
  • 5
    Blown fuse in the charger module low-voltage supply circuit.
  • 6
    CAN bus network interference or fault affecting multiple charging system modules.
  • 7
    Water ingress into the charger module or its connector.

Symptoms drivers notice

Vehicle cannot initiate or complete an AC charging session.
Charging system warning or plug-in charge unavailable message in the instrument cluster.
Scan tool cannot communicate with the on-board charger module.
High-voltage battery state of charge remains unchanged when plugged in.
Other high-voltage system communication faults may be present alongside U0D97.

How to diagnose U0D97

A typical diagnostic flow when this code is present.

  1. 1
    Follow all applicable high-voltage safety precautions before beginning diagnosis.
  2. 2
    Retrieve all DTCs from all modules; note co-set charging system or high-voltage codes.
  3. 3
    Verify 12V supply voltage and ground continuity at the on-board charger module connector.
  4. 4
    Inspect the charger module connector and harness for corrosion, water damage, or loose terminals.
  5. 5
    Check the charger module supply fuse in the fuse box.
  6. 6
    Measure CAN bus differential voltage at the module connector to confirm the bus signal is present.
  7. 7
    If power and bus signal are confirmed but no communication is possible, the charger module is likely failed; follow manufacturer replacement and programming procedures.

Related network codes

Frequently asked questions

Can U0D97 prevent the vehicle from driving, not just charging?

On some platforms yes, because the vehicle management system uses charging module status as part of the high-voltage system health check. If communication is lost and the system cannot confirm a safe state, a power reduction or no-start condition may be imposed.

Does U0D97 affect DC fast charging as well as AC charging?

DC fast charging typically uses a separate charging control path. U0D97 refers specifically to the on-board AC charger module. DC fast charging may use different module communication and would generate different network codes if affected.

Can a software update fix U0D97?

If the code was set due to a software bug in the charger module, a firmware update may resolve it. Check for applicable technical service bulletins before replacing hardware.

Is the on-board charger module the same as the inverter?

No. The on-board charger converts AC grid power to DC for battery charging. The inverter converts DC from the battery to AC for driving the electric motor. They are separate modules, each with their own communication nodes.

Disabling U0D97 in software

RaceTune can permanently disable U0D97 — 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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