P25F5 Turbocharger/Supercharger Boost Sensor C Circuit High

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.

Likely causes

Symptoms

• Check engine lamp on, depending on the manufacturer
• Reduced power, boost cut back

Repair estimate

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

Related codes

References: law.cornell.edu, saabwisonline.com, saabwisonline.com.