Powertrain, generic (extended)

P23A5 Exhaust Heat Exchanger Exhaust Bypass Valve B Control Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

Unlike the circuit codes, P23A5 judges the result: the module commanded valve B, the second exhaust bypass at the heat exchanger, but it does not see the response it expects, for example in position feedback or in how the exhaust-side coolant temperatures change. No manufacturer publishes P23A5. Ford's handling of valve A shows how such a check can mislead: for P237F on F-150, Explorer, Escape and Maverick full hybrids up to 2024, SSM 52543 first has the connectors of exhaust coolant temperature sensors 3 and 4 inspected for water or corrosion, and TSB 24-2173 cures false P237F on 2024 Mavericks with a PCM update. CARB requires a functional check of output components. Driving is usually unaffected; P23A6 and P23A7 name a flap stuck in one position.

Likely causes

Flap of valve B sluggish from soot or corrosion
Exhaust coolant temperature sensor connector wet or corroded, distorting the plausibility check
Worn actuator gearing or linkage
Overly strict calibration, fixed by a software update

Symptoms

  • Check engine light on
  • Cabin heat slow to arrive in winter
  • No effect on drivability

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€0–1,500
Time0.5–3 h

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

Parts involved

exhaust bypass valve bexhaust heat exchanger

Related codes

P23A2P23A6P23A7P23A8P237F

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