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.
High severity. Can I keep driving?Avoid driving if the light is flashing or the engine is shaking: unburned gasoline can damage the catalytic converter.
Cylinder 8 is numbered according to the manufacturer: check your engine's manual before working on it.
Symptoms
- Check engine light on
- Rough idle, shaking or knocking
- Loss of power or smoke
- Higher consumption, poor cold start
Most 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- Engine software outdated or diagnosis too sensitive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
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: hard
- It affects emissions.
What each character of P0284 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 2: Fuel injection
- 84: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0284?
Avoid driving if the light is flashing or the engine is shaking: unburned gasoline can damage the catalytic converter.
What causes code P0284?
The most common causes are: injector of cylinder 8 worn, coked or leaking; engine software outdated or diagnosis too sensitive; injector correction codes not or wrongly programmed after replacement.
Related codes
- P0308Cylinder 8 Misfire Detected
- P0208Cylinder 8 Injector A Circuit/Open
- P02DACylinder 8 Fuel Injector A Offset Learning At Min Limit
- P021BCylinder 8 Injection Timing
- P0287Cylinder 9 Contribution/Balance
Sources
- law.cornell.edu: 13 CCR 1968.2
- patents.google.com: US5385129
- fordservicecontent.com: obd summary diesel 2023
- gsi.ext.gm.com: 14OBDG10 Engine Diagnostics
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.