What is it for?

This control unit (often called LCM - Light Control Module or LED ballast module) is applied directly to the headlight body and is responsible for:

• Power supply and control of the LED diodes of the front headlights (low beam, high beam, DRL/position lights and direction indicators).
• Light regulation and beam management in systems with advanced LED projectors (e.g. IQ.LIGHT / Matrix LED).
• Interchangeability: It can be mounted on either the left or right headlight.

Technical note: Since this is a new-generation electronic component based on the MQB-Evo architecture, in the event of replacement, recoding or software adaptation (via ODIS-type diagnosis) is usually necessary to correctly match it to the chassis (VIN) and vehicle configuration.

Which cars is it used on?

The control unit is used on several recent models of the VAG Group (MQB and MQB Evo platforms, approximately from 2020 onwards):

BrandCompatible Models:

• Volkswagen Golf VIII (Mk8, including GTI, R, IQ.Light), Polo 6R/2G Facelift, T-Roc (Facelift), T-Cross, Taigo, Tayron
• CUPRA / SEAT Formentor, Leon IV (KL), Terramar
• Škoda Octavia IV, Kamiq, Scala, Superb (B9), Kodiaq II, Elroq

In most cases, the replacement of the 992.941.571.AH control unit (or similar VAG modules) is due to three main causes: water ingress, internal electrical faults or physical damage in an accident .

1. Water infiltration and humidity (Cause #1)

Being mounted directly in the rear or lower part of the headlight, it is the first to suffer the consequences of:

• Excessive condensation or cracks in the polycarbonate of the headlight.

• Missing caps or worn seals.

• Clogged headlight vent pipes.

Water or moisture collects on the connector and PCB (printed circuit board), causing rapid oxidation of the pins, short circuits and corrosion of the tracks .

2. Internal component failures (Wear & Tear)

Since it is a power module that works with high frequencies and currents to drive LED drivers, the internal components are subject to thermal and electrical stress:

• Overheating / Superheating: The failure of MOSFETs or voltage regulators due to continued heat.

• Voltage spikes: Electrical surges caused by dead batteries, jump starting, or alternator malfunctions.

• End-of-life of capacitors: Natural deterioration of SMD electronic components after thousands of hours of operation.

3. Road accidents or head-on collisions

Even in the event of minor/medium-sized impacts where the headlight does not appear to be destroyed:

• The control unit mountings or plastic casing may crack.

• The internal comb/pin connector may bend or break.

• The motherboard can suffer micro-fractures invisible to the naked eye that interrupt electrical continuity.

Typical symptoms that indicate the need to replace it

If the control unit fails, the car will usually exhibit one or more of these signs:

• Headlight completely off or partially non-functional (e.g. DRL/indicators active but low beam or high beam dead).

• Error message on the instrument panel: "High beam headlight failure" , "IQ.Light / Matrix LED failure" , "Headlamp levelling not available" .

• LEDs flickering or turning off suddenly after a few minutes of use.

• Matrix / Automatic High Beam function deactivated by the on-board system due to a communication error in the CAN bus.

Workshop advice: Before purchasing a new control unit, it's always recommended to swap the unit between the right and left headlights (if the other side is OK). If the problem shifts to the other side, the module is 100% confirmed to be faulty. If condensation has wet the headlight, it's essential to dry it and eliminate the cause of the leak before installing the new module, otherwise you risk quickly burning out the new one as well.