Hilux preheating lamp and smoke issue

The symptoms you describe do indeed suggest a potential issue with the glow plug control system. A continuously illuminated preheating lamp, coupled with the check engine light and excessive smoke, points towards a malfunction in the preheating cycle. The engine management system detects this anomaly and triggers the warning lights. Tell me, does the vehicle exhibit any starting difficulties, particularly when the engine is cold?

Yeah, it's a bit rough when it's cold. Does that confirm the control unit thing? Is it something I could fix myself or should I just take it in?

The cold start difficulties further corroborate the suspicion of a faulty glow plug control unit. Think of it like a pilot light in a furnace; if it's not working right, the whole system struggles to ignite. While replacing the unit itself is relatively straightforward, diagnosing the root cause – whether it's the unit, wiring, or plugs – requires specialized diagnostic equipment. Given the potential for misdiagnosis and further complications, consulting a qualified technician is advisable.

Thanks for the advice. Took it to a workshop, and you were spot on – turned out to be a defective cable/plug to the glow control unit. 95€ later, it's running perfectly again.