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BMW 1 Series: N47S 2.0L twin-turbo sequential-turbo failure (123d / 125d)

N47S 2.0L twin-turbo sequential-turbo failure (123d / 125d) is a common engine fault on the BMW 1 Series on the 2007–2016 cars, and we rate it major. Putting it right costs ≈A$1,380 to ≈A$5,060 at independent workshop rates, shown as an approximate guide in Australian dollars. Below is what goes wrong, the symptoms to notice on a test drive, where to look, and what to ask the seller before you hand over any money. It is one of 54 documented faults on the BMW 1 Series.

Vehicle
BMW 1 Series
Only on
Bi-Turbo / twin-turbo
Engine
N47
Years
2007–2016
Fuel
diesel
System
Engine

This page covers the BMW 1 Series as a model. Some faults only affect particular engines or build years — enter a plate below to narrow the list to one car.

All BMW 1 Series faults54 documented faults on this model

What you are looking at

No photograph available

We do not hold a verified photograph of the Turbocharger yet. We would rather show none than show a picture of a different part.

What goes wrong

The 123d/125d's headline feature is its sequential twin-turbo setup on the 2.0-litre N47S - a small and a large turbo working in stages. The extra turbo, its changeover flap and the electronic actuators are a known weak point: soot and age cause the actuator to stick and the vanes to clog, giving intermittent low boost and limp mode. It is a more failure-prone system than the single turbo on a base 120d/320d, and repairs are dearer because there are two turbos and their control hardware to consider.

What you would notice

  • Intermittent low boost / limp mode
  • Power returns after an ignition off-on cycle
  • Boost-pressure or turbo-actuator fault codes
  • Flat spot in the mid-range or lack of top-end pull

How to check it

Where to look. Sequential twin turbochargers and actuators on the exhaust side of the 2.0-litre engine

  1. On the drive, accelerate firmly through the rev range and confirm both turbo stages deliver smooth boost with no sudden drop or limp mode.

  2. Scan for boost/actuator codes.

  3. Ask whether either turbo, the changeover flap or an actuator has been replaced.

Parts involved: Turbocharger.

What it costs to put right

≈A$1,380 to ≈A$5,060 at independent workshop rates, shown as an approximate guide in Australian dollars. That is for this job on its own, not for the car.

An estimate, converted to Australian dollars, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

Ask the seller

  • “Does it ever lose boost or go into limp mode?”
  • “Have the turbos or turbo actuator been replaced?”

Now check the BMW 1 Series you are actually looking at

Everything above is true of the model, and it is free. What it does not tell you is whether THIS car still has money owing on it, has been written off or reported stolen, what kms it showed in past sale ads, whether it has had accident repair claims and what it is worth today. That comes from the official records for that plate. Enter the plate and its state for the A$17.90 Vehicle Check, or the full history from A$24.99.

Where this comes from

The failure described above is documented in the sources below. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them.

  • BabyBMW.net '125D recommendations' and 123d reliability threads
  • ECU Testing BMW turbo actuator problem page
  • PistonHeads 123d ownership/reliability discussion

BMW 1 Series buyer questions

Is n47s 2.0l twin-turbo sequential-turbo failure (123d / 125d) serious on a BMW 1 Series?

We rate it major and common on the BMW 1 Series. The 123d/125d's headline feature is its sequential twin-turbo setup on the 2.0-litre N47S - a small and a large turbo working in stages. The extra turbo, its changeover flap and the electronic actuators are a known weak point: soot and age cause the actuator to stick and the vanes to clog, giving intermittent low boost and limp mode. It is a more failure-prone system than the single turbo on a base 120d/320d, and repairs are dearer because there are two turbos and their control hardware to consider.

How much does it cost to fix on a BMW 1 Series?

≈A$1,380 to ≈A$5,060 at independent workshop rates, shown as an approximate guide in Australian dollars. That figure is for this job on its own. A car showing the symptoms on this page is usually worth either walking away from or negotiating down by at least the repair figure.

Which BMW 1 Series years are affected?

Our research records this fault on the 2007–2016 BMW 1 Series. Build dates move around, especially on imported cars, so treat the range as the years to look hardest at rather than a guarantee either way. The official records tell you the exact build and first registration date for the car in front of you.

How do I check for it before I buy?

On the drive, accelerate firmly through the rev range and confirm both turbo stages deliver smooth boost with no sudden drop or limp mode. Scan for boost/actuator codes. Ask whether either turbo, the changeover flap or an actuator has been replaced. Look here: Sequential twin turbochargers and actuators on the exhaust side of the 2.0-litre engine