P25F5 reports a signal from boost sensor C above the highest plausible value. Since the voltage climbs with pressure, a reading at the top end usually means an electrical fault: the signal shorted to 5 V or battery voltage, an open sensor ground, or an open signal wire where the input is pulled up. The limits differ widely by engine – for sensor A, Saab's GM-based 1.6 litre sets its code above 4.8 V (4 s at a stretch or 50 s cumulated, type C without lamp), whereas the 2.0 litre already flags a reading above 3.9 V lasting 5 s as a type B fault. No manufacturer documents these limits for sensor C. Because the engine would believe boost is excessive, it typically cuts boost control. P25F4 is the opposite fault.
Medium severity. Can I keep driving?Drive without demanding power and go to a repair shop soon. If you see a lot of blue smoke or hear a metallic noise, shut off the engine.
Symptoms
- Check engine lamp on, depending on the manufacturer
- Reduced power, boost cut back
Most likely causes
- Sensor ground open or high resistance
- Signal wire shorted to 5 V or battery voltage
- Boost sensor C failed internally
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It can trigger limp mode.
- It affects emissions.
What each character of P25F5 means
- P: Powertrain: engine and transmission
- 2: Generic code: same on every make
- 5: Speed and idle
- F5: Specific fault in that system
Frequently asked questions
Can I keep driving with code P25F5?
Drive without demanding power and go to a repair shop soon. If you see a lot of blue smoke or hear a metallic noise, shut off the engine.
What causes code P25F5?
The most common causes are: sensor ground open or high resistance; signal wire shorted to 5 V or battery voltage; boost sensor C failed internally.
Related codes
- P25F2Turbocharger/Supercharger Boost Sensor C Circuit
- P25F3Turbocharger/Supercharger Boost Sensor C Circuit Range/Performance
- P25F4Turbocharger/Supercharger Boost Sensor C Circuit Low
- P0238Turbocharger/Supercharger Boost Sensor A Circuit High
- P0242Turbocharger/Supercharger Boost Sensor B Circuit High
Sources
- law.cornell.edu: 13 CCR 1968.2
- saabwisonline.com: dtc p0237 or p0238 llu
- saabwisonline.com: dtc p0236 p0237 or p0238
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.