Powertrain, generic (extended)

P25F3 Turbocharger/Supercharger Boost Sensor C Circuit Range/Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P25F3 means boost sensor C delivers a signal that is electrically valid but does not agree with what the other pressure readings and the engine model suggest. Saab's 2.0 litre turbo engine, developed with GM, shows how this is checked for sensor A: with the engine stopped the reading must lie between 50 and 115 kPa, roughly matching barometric pressure, and while running it is compared with a model built from barometric, manifold and throttle-inlet pressure and throttle position; a failure is a two-trip type B code. A comparable check would apply to C. Typical reasons are a leak or blocked port at the measuring point, oil fouling and sensor drift. No manufacturer publishes this code for sensor C. Expect reduced boost and a lamp.

Likely causes

Charge air leak near the measuring point of sensor C (hose, clamp, seal)
Sensor port fouled by oil from crankcase ventilation or a drifting sensor
Faulty barometric or manifold pressure sensor skewing the comparison

Symptoms

  • Check engine lamp on
  • Reduced power under load
  • Hissing noise if a charge air leak is present

Repair estimate

DifficultyMediumDIY possible
Parts and labour€30–400
Time0.5–3 h

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

Parts involved

boost pressure sensor csensing line

Related codes

P25F2P25F4P25F5P0236P0240P2CD7

References: law.cornell.edu, saabwisonline.com, en.wikipedia.org.