Powertrain, generic (extended)

P21D9 Cylinder 11 Injector B Circuit/Open

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P21D9 is reserved for an open circuit of the second injector on cylinder 11 and therefore only makes sense on twelve-cylinder engines with dual injection. No manufacturer documents this code publicly, and no available source names a twelve-cylinder engine that uses it. Its meaning follows from the series: like P21CF to P21D6, it is an electrical check of the injector drive, not of fuel quantity. CARB requires such circuit monitoring for injectors whose failure affects emissions; Ford's documented B-injector check for up to eight cylinders runs continuously above 11 V and needs 5 s, which shows the typical scale. If it ever appears, check the injector coil resistance and the harness first. The direct counterpart in the A series is P020B, the misfire code for cylinder 11 is P0311.

Likely causes

Open coil in the second injector of cylinder 11
Damaged injector harness or loose plug
Faulty driver in the engine control module

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

P020BP21F0P21F1P21D8P21DAP0311

References: law.cornell.edu, fordservicecontent.com.