Powertrain, generic (extended)

P23FD Cylinder 12 Injector B Air-Fuel Ratio Imbalance

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modeNo

P23FD closes the cylinder series at number 12. It states that the twelfth cylinder runs out of step with the rest and that the cause lies with its injector B. A matching engine needs twelve cylinders and two injectors in each, a combination that public engine references do not show: the VW W12, for instance, appeared with port injection and later as the 6.3 FSI with direct injection only. CARB nonetheless expects every petrol engine to detect imbalance that would lift emissions beyond the limits, and lets the stored code stay at bank or misfire level when the method cannot single out one cylinder. No manufacturer documents P23FD. On a V12 or W12 that stores it, compare the bank codes P23FE/P23FF and P219A/P219B with P21A7, P0312 and P21DA.

Likely causes

Second injector of cylinder 12 out of tolerance

Intake leak or valve sealing fault at cylinder 12

Code reported by a tool on an engine without a second injector

Symptoms

Check engine light on
Bank or misfire code stored at the same time

Repair estimate

DifficultyShop_onlyWorkshop job

Parts and labour€200–1,800

Time2–10 h

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

Parts involved

fuel injector b cyl 12

Related codes

P21A7 P21DA P0312 P23FC P23FE P23FF

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