Preheating light flashes – this may be the problem

Headlight flashing – possible causes

You should react immediately as soon as you notice that the light is flashing:

• If the preheating light flashes, in many cases there is a problem in the exhaust gas recirculation system. This can have very different causes, but you should visit a good garage as soon as possible and have the problem checked.
• The fault memory of your vehicle can be read out there an essential step in identifying the exact cause. The fault memory often provides typical fault codes, such as the code P0380, which indicates problems with the glow plug control unit.
• In the case of diesel, the installed particulate filter is also a possible reason for the flashing light. It is possible that the particulate filter is clogged and can no longer work properly. The engine then switches to emergency mode and no longer accelerates as before. The particulate filter usually needs to be replaced at around 120,000 kilometers. Alternatively, cleaning with a special foam is also possible under certain conditions.
• Another common cause is a malfunction in the preheating system itself, for example due to defective glow plugs or a faulty glow control unit. These components are responsible for preheating the engine, especially in cold temperatures. A defect can lead to starting problems and also trigger the indicator light to flash.
• Marten damage is also one of the typical triggers – for example, if cables, sensor lines or insulation in the engine compartment have been damaged. Such damage can also lead to malfunctions in the engine management system.
• In addition, many different sensors can cause the problem. Triggering sensors include, for example, the accelerator pedal position sensor, the crankshaft sensor, the differential pressure sensor or the exhaust gas temperature sensor.
  Problems in these areas can disrupt the interaction within the engine management and the drive-by-wire system and thus trigger the warning signal.

• Rarely are defective brake lights or a faulty brake light switch to be mentioned as triggers. Nevertheless, there may also be a connection here. In this case, check whether the brake lights light up as usual when the brakes are applied – for example with the help of a reflective surface or with the assistance of a second person.
• Note: We strongly advise you to visit a workshop as soon as the pre-brake light flashes. There are many different causes, and it is difficult for laypersons to identify the exact trigger. At the workshop, not only will the fault memory be read out, but you will also receive sound recommendations for the next steps and any necessary repairs.