Powertrain, generic (extended)

P21A7 Cylinder 12 Air-Fuel Ratio Imbalance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P21A7 is the last code of the cylinder series that starts with P219C and points to cylinder 12 of a twelve-cylinder engine. There is no public manufacturer description and no NHTSA bulletin for it. Under CARB's rule (13 CCR 1968.2 (e)(6.2.1)(C)) the monitor had to be in all 2014 and later petrol vehicles, with limits of 3.0 times the FTP standard until 2014 and 1.5 times from 2015 for non-LEV III cars, so twelve-cylinder engines are covered as well; many simply report the bank code P219A or P219B. The causes do not differ from smaller engines: a single injector, a leaking intake seal or a valve that does not close properly. Because a V12 has two separate banks, check whether the bank code and the misfire counter P0312 agree with cylinder 12 before parts are replaced.

Likely causes

Cylinder 12 injector out of tolerance
Intake seal leak at cylinder 12
Valve not sealing at cylinder 12

Symptoms

  • Check engine light on
  • Possible P0312 or slight vibration

Repair estimate

DifficultyHardWorkshop job
Parts and labour€0–3,000
Time1–10 h

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

Parts involved

fuel injector

Related codes

P219AP219BP21A6P0312

References: law.cornell.edu, patents.google.com.