U0624

Lost Communication With High Beam Control Module

U0624 is a generic OBD-II network diagnostic trouble code: Lost Communication With High Beam 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
U0624
Group
Network
System
Network
Severity
Warning (MIL on)
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What U0624 means

U0624 is logged when the network master or a peer module no longer receives expected messages from the High Beam Control Module. On vehicles that separate low-beam and high-beam electronics into distinct control units, this module handles automatic high-beam activation, camera-based glare detection, and in some implementations LED high-beam driver logic.

The fault mechanism is identical to other lost-communication codes: the receiving module detects an absence of periodic network frames from the High Beam Control Module beyond a configurable timeout. This can occur due to a wiring fault on the bus segment, loss of module power, connector damage, or an internal module failure.

Operationally, U0624 disables automatic high-beam control; most vehicles revert to manual high-beam operation or disable high beams entirely as a fail-safe. Other safety systems that use the same forward-facing camera or bus segment may also be degraded, so a thorough scan for companion codes is important before beginning electrical diagnosis.

Common causes

Most-frequently reported root causes when U0624 is logged.

  • 1
    Open or short circuit on the CAN or LIN segment connecting the High Beam Control Module.
  • 2
    High Beam Control Module power supply fuse blown.
  • 3
    Corroded or damaged wiring harness connector at the module.
  • 4
    Internal failure of the High Beam Control Module.
  • 5
    BCM or gateway port failure disrupting downstream LIN communication.
  • 6
    Water intrusion into the module housing via the headlamp assembly.
  • 7
    Incompatible or incorrectly programmed replacement module.

Symptoms drivers notice

MIL or driver assistance warning illuminated.
Automatic high-beam function inoperative.
High beams may be locked out or require manual override.
Companion camera-based ADAS codes may be present simultaneously.
Scan tool does not see the High Beam Control Module on the network.

How to diagnose U0624

A typical diagnostic flow when this code is present.

  1. 1
    Retrieve all stored codes with a scan tool before clearing; note any companion network or ADAS codes.
  2. 2
    Check whether the High Beam Control Module appears in the module list of the scan tool.
  3. 3
    Verify module supply voltage and ground integrity at the connector.
  4. 4
    Inspect headlamp connector and module housing for moisture or corrosion.
  5. 5
    Test bus signal continuity between the module connector and the BCM or gateway.
  6. 6
    If using a LIN sub-bus, verify the BCM LIN master output is generating a valid wake signal.
  7. 7
    Replace the module only after ruling out all wiring and power faults.

Related network codes

Frequently asked questions

Can U0624 disable lane-keep or adaptive cruise?

Possibly. If the forward camera shares a bus with the High Beam Control Module and the fault disrupts that segment, companion ADAS systems may also degrade.

Will the vehicle pass inspection with U0624 stored?

In most jurisdictions an active MIL will cause an OBD inspection failure regardless of whether the underlying fault is emissions-related.

Is U0624 the same as U0623?

No. U0623 targets the general Headlamp Control Module while U0624 specifically targets a separate High Beam Control Module; some vehicles have both, others only one.

Can a software update fix U0624?

Sometimes. Manufacturers occasionally release BCM or module calibration updates that correct bus timing mismatches causing false lost-communication faults.

Disabling U0624 in software

RaceTune can permanently disable U0624 — 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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