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

P0284 Cylinder 8 Contribution/Balance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P0284 comes from the cylinder balance control of common-rail diesels: the engine module measures the crankshaft acceleration of each cylinder's power stroke, compares it with the average and gives a deviating cylinder more or less fuel. The code sets when the correction for cylinder 8 reaches its limit and the cylinder still does not keep up – GM at 95 % of a limit of about ±12–17 mm³ for 30 s, Ford above 90 % of the allowed 3.5–15 mg per stroke for 7.5 s; GM needs two trips. The code does not say whether there is too much or too little fuel – the correction value for cylinder 8 shows the direction: strongly negative means a leaking injector, strongly positive a weak injector or low compression.

Likely causes

Injector of cylinder 8 worn, coked or leaking
Engine software outdated or diagnosis too sensitive
Injector correction codes not or wrongly programmed after replacement
Low compression on cylinder 8 (valve, rings, injector seal)
Crankshaft sensor or tone wheel learning faulty, dual-mass flywheel

Symptoms

  • Check engine light on
  • Rough idle, shaking or knocking
  • Loss of power or smoke
  • Higher consumption, poor cold start

Repair estimate

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

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

Parts involved

fuel injector cylinder 8crankshaft position sensorengine control module

Related codes

P0308P0208P02DAP021BP0287

References: law.cornell.edu, patents.google.com, fordservicecontent.com, gsi.ext.gm.com.