P0045–P004A Turbocharger/Supercharger Boost Control A Circuit/Open
The circuit is broken somewhere - a cut wire, a corroded pin or an unplugged connector means the signal never arrives.
Can you drive it? The car is most likely in limp mode with boost cut. It is drivable gently, but it will not make full power and should not be driven hard until it is fixed.
Which code is which
Same fault, different cylinder or bank — diagnosed the same way. Several set together usually means one shared cause.
| Code | Definition | Severity |
|---|---|---|
P0045 | Turbocharger/Supercharger Boost Control A Circuit/Open | Investigate soon |
P004A | Turbocharger/Supercharger Boost Control B Circuit/Open | Investigate soon |
The definition
P0045: Turbocharger/Supercharger Boost Control A Circuit/Open.
P0045 is a powertrain code (the engine or gearbox), defined by the SAE standard - it means the same thing on any make of car, and any generic OBD-II reader will decode it.
What to check first
Cheapest and fastest checks first:
- Check the connector is fully seated and the locking tab is engaged. A half-seated plug is the single most common cause of an open circuit.
- Back-probe the pins and check continuity from the part back to the module connector.
- Inspect for a pushed-back or corroded terminal - the wire looks fine but the pin has backed out of the housing.
Reading the code is the easy part
A code names the circuit that complained. What tells you why is watching the sensor behind it while the engine runs — and that is where a code reader stops and a diagnostic tool starts.
VAGPULSE reads every module in a VW, Audi, Skoda or SEAT — not just the engine — shows the live measuring blocks behind this fault, gives you the freeze-frame conditions it was logged under, and clears it once you have fixed it. It also does what a generic OBD reader cannot on a VAG: service resets, coding, adaptations, and Stage 1–3 flashing with your original file saved first.
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Common questions
What does P0045 mean?
P0045 means Turbocharger/Supercharger Boost Control A Circuit/Open. The circuit is broken somewhere - a cut wire, a corroded pin or an unplugged connector means the signal never arrives.
Can I drive with P0045?
The car is most likely in limp mode with boost cut. It is drivable gently, but it will not make full power and should not be driven hard until it is fixed.