Mercedes ML Diesel Glow Plug Issue

Those symptoms point to a failing glow plug, common in older diesels. The stored error code and persistent lamp make it likely that one or more are defective. Do you notice any engine misfire, especially during cold starts? Is the engine light on too? Knowing this helps narrow it down. A bad glow plug will keep the preheating lamp on and trigger an error. If you have tools and some skill, you could test the plugs with a multimeter, checking resistance, but disconnect the battery first. If you are not comfortable with electrical testing, get professional help. Also, how many glow plugs does your diesel engine have?

Yes, I have noticed slight engine misfire, especially during cold starts. The engine light is also illuminated. My electrical testing skills are limited, so I plan to seek professional help. What are the potential implications of driving with a defective glow plug, even a short distance to the workshop? Also, what is the number of glow plugs fitted to the Mercedes ML 2007 diesel engine?

The misfire and engine light reinforce the likelihood of a defective glow plug. I would be cautious and minimize driving until it's fixed. Driving too long with a bad glow plug can cause incomplete combustion, increased emissions, and damage to the diesel particulate filter (DPF), if equipped. Your diesel engine will have either 4, 5 or 6 glow plugs. It depends on the particular engine you have. Typically it will be one for each cylinder. I strongly advise against attempting to rectify the issue yourself, particularly given your limited experience with electrical testing. I suggest that you take your vehicle to a qualified workshop for diagnosis and repair. The estimated repair cost of 440€ appears to be reasonable, assuming it includes the replacement of all glow plugs and associated labor charges.

I appreciate your guidance and recommendations. I've decided to take it to a workshop. They confirmed the glow plugs are defective and quoted 440€, as expected. Thanks again for your help.