Peugeot 5008 Preheating Control Unit Issue

I had something similar with my 5008. The preheating lamp issue and check engine light combo sounds familiar. Did you check the resistance of the glow plugs themselves? Sometimes a faulty glow plug can throw the whole system off. But the smoke on acceleration is a bit concerning, could be related or something else.

I'm not sure how to check the resistance of the glow plugs, I don't have the right tools or know the correct range. Is there an easy way to tell if that's the problem?

Without the right tools, it's tricky. Don't poke around too much if you're not comfortable. Given the smoke, and if you suspect the preheating control unit or its connections anyway, a workshop visit might be best. They can properly diagnose the issue and prevent further damage. I ended up replacing a faulty preheating control unit and cleaning some connections, which sorted the problem.

I took your advice and went to the workshop. You were spot on – it was indeed the preheating control unit and a dodgy cable connection! The repair cost me 95€, but at least the problem is sorted. Now the preheating lamp is behaving itself, no more check engine light, and thankfully, the smoke is gone. Thanks again for pointing me in the right direction!