U059F

Lost Communication With Headlamp Control Module

U059F is a generic OBD-II network diagnostic trouble code: Lost Communication With Headlamp 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
U059F
Group
Network
System
Network
Severity
Information only
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What U059F means

U059F is set when the BCM or a gateway module loses all communication with the Headlamp Control Module (HCM). The HCM manages functions such as adaptive driving beam control, automatic high-beam switching, headlamp leveling, and light-on reminder logic. Loss of communication with this module does not affect powertrain operation but can disable advanced lighting features.

On vehicles where the HCM is integrated with the forward-facing camera or adaptive front-lighting system, U059F may also be accompanied by codes for other camera-dependent features such as lane-keeping and automatic emergency braking, since these systems often share a module or bus segment with the HCM.

The code is typically stored in the BCM or central gateway and the headlamps themselves often default to a fixed low-beam state for safety. Diagnosis should focus on power, ground, and LIN/CAN bus integrity in the headlamp assembly area, as these modules are frequently exposed to moisture and vibration.

Common causes

Most-frequently reported root causes when U059F is logged.

  • 1
    Failed Headlamp Control Module within the headlamp assembly.
  • 2
    Water or condensation ingress into the headlamp housing damaging the internal module.
  • 3
    Open or short circuit in the LIN or CAN bus wiring to the HCM.
  • 4
    Loss of power or ground to the headlamp assembly.
  • 5
    Corroded connector pins on the headlamp harness plug.
  • 6
    Physical damage to the headlamp assembly from collision or road debris.
  • 7
    Blown fuse for the headlamp control circuit.

Symptoms drivers notice

Adaptive high-beam or automatic lighting features disabled.
Headlamp leveling motor may not respond to load changes.
Headlamps may default to a fixed position or fixed intensity.
U059F stored in BCM or gateway module memory.
Companion codes for camera or ADAS features may also be present.

How to diagnose U059F

A typical diagnostic flow when this code is present.

  1. 1
    Read all stored DTCs across BCM, gateway, and ADAS modules.
  2. 2
    Inspect the headlamp assembly and connector for moisture, corrosion, or physical damage.
  3. 3
    Verify supply voltage and ground at the headlamp harness connector.
  4. 4
    Check the fuse for the HCM circuit.
  5. 5
    Test LIN or CAN bus wiring continuity between the BCM and the headlamp connector.
  6. 6
    Clear codes and test all headlamp modes (auto, high beam, leveling) to assess functionality.
  7. 7
    Replace the headlamp assembly if the internal HCM is confirmed failed and wiring checks are satisfactory.

Related network codes

Frequently asked questions

Will headlamps still work with U059F active?

Typically yes, but only in a fixed default state. Adaptive, automatic, and leveling functions will be disabled.

Why does water in the headlamp cause U059F?

Modern headlamp assemblies contain integrated control modules; moisture reaching these electronics can cause internal failure and loss of bus communication.

Can U059F disable lane-keeping or emergency braking?

On platforms where ADAS cameras share a module or bus segment with the HCM, yes; always check for companion ADAS codes.

Is the fix typically a new headlamp assembly?

Often yes, because the HCM is integrated and not separately serviceable on most platforms; however, always verify wiring first.

Disabling U059F in software

RaceTune can permanently disable U059F — 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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