Mercedes GLE diesel glow plug issue

That sounds familiar. A defective glow control unit can definitely cause those symptoms. The glow plugs are crucial for starting, especially in colder weather, so if the control unit isn't working right, the engine might struggle and produce smoke until it warms up. Check the wiring and connectors going to the glow control unit. Sometimes, a loose or corroded connection is the culprit. A diagnostic test should pinpoint the fault though.

Where should I look for these wiring and connector issues? I'm not experienced with car maintenance, but I'm willing to take a look before going to a professional. Also, would a faulty connection consistently trigger the check engine light, or could it be intermittent?

The glow control unit is usually located somewhere near the engine, often on the inner fender well or near the ECU. The wiring will run from the control unit to each individual glow plug. Look for any signs of damage to the wires themselves like cracks, fraying, or melting. The connectors should be firmly attached and free from corrosion. A faulty connection can definitely trigger the check engine light consistently, especially if the ECU detects an open circuit or short circuit in the glow plug system. Given your description, I'd advise getting it checked at a workshop to avoid further damage. They can perform a more thorough diagnostic test.

Thanks for the advice. I will schedule an appointment with my trusted workshop to have the glow control unit and wiring inspected. I will have them perform a comprehensive diagnostic test to confirm the issue and ensure no further complications exist. It turned out to be a defective plug connection to the glow control unit. They cleaned the connection and the issue is resolved. The repair cost was 95€.