Powertrain, generic (extended)

P2BF8 Exhaust Flow Control Valve B Control Circuit/Open

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

Valve B is the second exhaust flap; Ford's gasoline OBD summaries 2020-2024 put it on bank 2, while valve A (P26C5) serves bank 1. P2BF8 reports that the drive circuit for flap B is open or unusable. On Ford a smart driver checks the output continuously and flags it within about 5 seconds; the 2024 summary files the open circuit as subtype 13. GM's 2023 and 2024 OBD tables (23OBDG07, 24OBDG07) watch the PWM control line of an exhaust valve the same way: open circuit, battery above 9 V, 4 seconds, two trips to the MIL. Ford names P2BF8 in its Mustang active exhaust bulletins, and 25-2144 for F-150 trucks with the 5.2 L engine, model years 2023 to 2025, lists P2BF8:78, an actuator that fails alignment, which a PCM update and relearn resolve. A broken wire or unplugged actuator is the usual find.

Likely causes

Broken or unplugged harness to the bank 2 flap actuator
Open circuit inside the flap actuator
Actuator not aligned after replacement or outdated PCM software (subtype 78)

Symptoms

  • Check engine light on
  • Exhaust mode not available message
  • One tailpipe flap no longer moves

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–1,200
Time0.4–3 h

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

Parts involved

exhaust flow control valve bwiring harnessecm

Related codes

P2BF9P2BFAP2BFBP26C5P2D12

References: fordservicecontent.com, fordservicecontent.com, gsi.ext.gm.com, static.nhtsa.gov.