Powertrain, generic (extended)

P21ED Cylinder 9 Injector B Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P21ED is defined for a B injector circuit on cylinder 9 that reads high, meaning the control side is shorted to supply or, on some designs, the two injector wires touch. No manufacturer publishes thresholds or vehicles for it. Only engines with ten or more cylinders and dual injection could set it; Lamborghini's Huracán V10 with direct plus multi-point injection is the documented example, although its A/B naming is not public. CARB requires that an output component be flagged when it does not respond properly to commands, which is exactly the case here: the injector cannot be switched, so cylinder 9 depends on its other injector alone. Lean running at loads where both injectors work together is the likely result. Low fault: P21EC; A injector high fault: P0286.

Likely causes

Control wire of the cylinder 9 B injector shorted to power
Both injector wires bridged in the harness
Injector coil shorted internally
Driver stage in the control unit faulty

Symptoms

  • Check engine light on
  • Cylinder 9 lean in mixed injection operation
  • Misfire on cylinder 9 (P0309)

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

P21ECP21D7P0286P21EBP21EFP0309

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