Powertrain, generic (extended)

P21F2 Cylinder 12 Injector B Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P21F2 is the generic code for a low circuit state, usually a grounded control wire, at the B injector of cylinder 12. It would need a twelve-cylinder engine with two injectors per cylinder, and none could be documented: the V12s from Lamborghini and Aston Martin inject into the ports only. No manufacturer publishes the code in this sense. One maker does use the number differently: McLaren bulletin KA-01931 lists P21F205 and P21F22F on the Artura, a V6 plug-in hybrid, as high-voltage battery faults (safety design current too low/high), repaired by replacing battery parts. On an Artura it is therefore a battery fault, not an injector fault. For a genuine injector fault, CARB's circuit monitoring applies, and GM's V8 criteria (ground short below 0.5 Ohm) are a guide. High fault: P21F3.

Likely causes

Cylinder 12 B injector wire shorted to ground
Injector with internal ground fault
Manufacturer-specific use of the number (McLaren Artura high-voltage battery)

Symptoms

  • Check engine light on
  • Misfire on cylinder 12 (P0312)
  • Hybrid warning instead, if the code is a McLaren battery fault

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

P21F3P21DAP0294P21F0P0312

References: law.cornell.edu, static.nhtsa.gov, en.wikipedia.org, gsi.ext.gm.com.