P25F4
Turbocharger/Supercharger Boost Sensor C Circuit Low
The third boost pressure sensor signal is below the lower diagnostic threshold. Usually a shorted sensor element or a short to ground.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: medium
Symptoms
- Check engine light on
- Significant power loss / limp mode
- Possible blue or black smoke from exhaust
- Whistling or hissing sound from intake
Common causes
Ordered by how often each turns out to be the cause.
- Internal short in the sensor elementCommon
- Signal wire shorted to groundPossible
- Connector pins corroded - high contact resistanceLess likely
Parts involved
- Boost Pressure Sensor C
- Wiring Harness
P25F4 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.