Powertrain, generic · Fuel and air metering (injector circuit)

P021B Cylinder 8 Injection Timing

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P021B reports a fault in the injection timing of cylinder 8 on a diesel engine. Unlike P01D9/P01DA ('over retarded/advanced', the result of the injector learning routine in overrun), this code has no direction, and what it checks is up to the manufacturer. GM uses it as an electrical check on the 6.6 litre L5P Duramax V8: at every injection the engine module measures how long the injector current takes to reach its pull-in level of 13 A. If on the V8 that time is outside 60–150 µs in 10 of 20 samples, the code sets and the warning light comes on in the first trip. For 2020–2021 Silverado/Sierra HD, GM issued a software update against false setting. FCA's V6 and Ford do not use it.

Likely causes

Injector of cylinder 8 faulty (coil, armature, wear, deposits)
Injector wiring or connector: contact resistance, corrosion, chafing
Engine software sets the code falsely (update available for some models)
Injector driver stage or boost voltage in the engine module
Wrong injector code, contaminated fuel or loose injector clamp

Symptoms

  • Check engine light on
  • Rough running or misfire, rough idle
  • Loss of power, smoke or knocking possible

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–1,200
Time0.5–4 h

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

Parts involved

fuel injector cylinder 8injector wiringengine control module

Related codes

P01D9P01DAP0208P02DAP0308

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