Powertrain, generic (extended)

P21F0 Cylinder 11 Injector B Circuit Low

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modeNo

P21F0 is reserved for a low state, typically a wire touching ground, in the B injector circuit of cylinder 11. Setting it requires at least eleven cylinders with two injectors each, so in practice a V12 or W12 with combined port and direct injection. No such engine could be confirmed: Lamborghini's V12 family uses multi-point injection only, as do Aston Martin's V12 and Mercedes-AMG's M279. Accordingly no manufacturer documents the code. If a scan tool still shows it, check the cylinder count and whether the maker uses the number for something else. The generic logic follows CARB's circuit monitoring of output components; GM's V8 shows how it is usually judged (short to ground below 0.5 Ohm with the driver off). Open circuit: P21D9; high fault: P21F1.

Likely causes

Cylinder 11 B injector wire shorted to ground

Injector with internal short to ground

Code read on an engine without a cylinder 11 B injector (scan tool or maker-specific use)

Symptoms

Check engine light on
Misfire on cylinder 11 (P0311)

Repair estimate

DifficultyHardWorkshop job

Parts and labour€150–1,200

Time1–5 h

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

Parts involved

fuel injectorinjector wiringengine control module

Related codes

P21F1 P21D9 P0291 P21EE P21F2 P0311

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