Transit Reduced Engine Power

I had a similar issue with my 2018 BMW 3 Series. Dashboard light, same symptoms. Aftermarket ECU mods interfered with the engine management system. Have you checked the chip's wiring harness?

Thanks. Any specific area or diagnostic procedure you'd recommend to check the wiring harness?

My issue was improper grounding of the chip tuning module. Start by visually inspecting the grounding points, then do a continuity test. Given the error code, a workshop with car diagnostic experience is advisable.

It was the chip tuning. The workshop confirmed faulty grounding and recalibrated the ECU, repair cost 180€. Everything's normal now.