Powertrain, generic (extended)

P23A8 Exhaust Heat Exchanger Exhaust Bypass Valve B Position Sensor Stop Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P23A8 concerns the position feedback of exhaust bypass valve B at its mechanical end stops. Systems with a position sensor learn the readings at the fully open and the fully closed stop and compare later readings with them; if a stop value drifts out of its window, or the flap no longer reaches the stop at all, this code is set. Causes range from a carbon-fouled or bent flap to a slipping sensor or a worn actuator. No manufacturer documents P23A8; for valve A the equivalent is P25D6. Ford lists the valve A position sensor code P2C23 together with corroded exhaust coolant temperature sensor connectors (SSM 52543) and with a worn heat exchanger actuator (SSM 53003). CARB requires rationality checks on such inputs. Driveability normally stays unchanged.

Likely causes

Deposits or a bent flap keep valve B from reaching its end stop
Position sensor in the actuator drifted or loose
Play in the actuator gearing
End stops not relearned after a repair

Symptoms

  • Check engine light on
  • Valve position in live data does not reach the expected end value

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€0–1,200
Time0.5–3 h

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

Parts involved

exhaust bypass valve bexhaust heat recovery actuator

Related codes

P23A5P23A6P23A7P25D6P2C23

References: law.cornell.edu, static.nhtsa.gov, static.nhtsa.gov.