Powertrain, generic (extended)

P21D6 Cylinder 8 Injector B Circuit/Open

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P21D6 is the highest B injector code that any manufacturer documents publicly: both Ford's port injector check (P21CF to P21D6) and GM's LT5 injection module list end here. On the LT5 the port injectors exist to add fuel under boost beyond what the direct system and its mechanical pump can deliver, so an open cylinder 8 injector shows up mainly at high load, where that cylinder can run lean and lose power; GM stores the fault as Type A from 20 failed samples out of 25 with at least 11 V on the powertrain relay. In GM's firing order cylinder 8 follows cylinder 1. On Ford's 5.0 V8 from 2018 it is the rear cylinder of the second bank and the check runs continuously for 5 s. The direct injector counterpart is P0208; P21D5 is cylinder 7.

Likely causes

Port injector of cylinder 8 open
Wire damage at the rear of the engine near the firewall
Output of the engine or separate injection module failed

Symptoms

  • Check engine light on
  • Misfire or lean running on cylinder 8 under load
  • Power loss at wide-open throttle

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€100–800
Time1–4 h

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

Parts involved

fuel injectorinjector wiringengine control module

Related codes

P0208P21EAP21EBP21D5P21D7P0308

References: gsi.ext.gm.com, lsxmag.com, fordservicecontent.com, en.wikipedia.org.