P259F
Turbocharger A Boost Control Position At High Limit
The boost-control actuator on turbo A has been operating at the high end of its travel — the controller is saturated against the upper stop trying to bleed off boost. Indicates either a wastegate stuck closed, oversized turbo for the calibration, or commanded boost limits being exceeded by ambient conditions (cold dense air).
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: hard
Symptoms
- Charge status indicator shows fault
- Charging may not start or interrupts
- Slower-than-expected charge rate
Common causes
Ordered by how often each turns out to be the cause.
- Wastegate stuck closedCommon
Parts involved
- Turbo Actuator A
- Wastegate
P259F is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.