P0284

Cylinder 8 Contribution/Balance Fault

P0284 is a generic OBD-II powertrain diagnostic trouble code: Cylinder 8 Contribution/Balance Fault. It is logged by the engine control unit when the fuel/inj monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P0284
Group
Powertrain
System
Fuel/Inj
Severity
Warning (MIL on, possible limp mode)
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What P0284 means

P0284 — Cylinder 8 Contribution/Balance Fault — is set when the PCM determines that cylinder 8 is not generating the expected share of crankshaft acceleration during its power stroke. The PCM continuously monitors crankshaft speed increments for each cylinder; when cylinder 8 falls below the calibrated threshold, P0284 is stored. This fault can only occur on engines with eight or more cylinders — V8, V10, V12, and I8 — and is irrelevant to four- or six-cylinder platforms.

Fuel delivery problems are the most frequent root cause: a clogged, stuck, or failed fuel injector on cylinder 8 delivers the wrong fuel quantity, reducing combustion pressure and thus crankshaft acceleration. Ignition system faults — a worn spark plug, weak or failed coil-on-plug, or cracked ignition wire — yield the same crankshaft signature. Mechanical causes such as low compression from worn piston rings, damaged valves, or a blown head gasket specific to cylinder 8 will also cause P0284, as will a lean condition from a vacuum leak near the cylinder 8 intake port.

P0284 frequently appears alongside P0308 (Cylinder 8 Misfire). Because the code indicates that cylinder 8 is underperforming rather than simply showing an electrical fault, the diagnostic process must systematically evaluate fuel, ignition, and mechanical systems before any components are replaced. Delayed repair risks progressive engine damage and catalytic converter failure.

Common causes

Most-frequently reported root causes when P0284 is logged.

  • 1
    Failed, clogged, or stuck fuel injector on cylinder 8 delivering insufficient or no fuel.
  • 2
    Fouled, worn, or incorrectly gapped spark plug on cylinder 8 preventing complete combustion.
  • 3
    Weak or failed ignition coil or coil-on-plug for cylinder 8 reducing spark energy.
  • 4
    Low compression in cylinder 8 due to worn piston rings, damaged valves, or a leaking head gasket.
  • 5
    Vacuum or intake manifold leak near cylinder 8 creating a lean mixture in that bore.
  • 6
    Damaged or corroded injector wiring causing intermittent fuel delivery to cylinder 8.
  • 7
    PCM software fault causing incorrect crankshaft acceleration calculation for cylinder 8.

Symptoms drivers notice

MIL illuminated with P0284 stored, often alongside P0308 (Cylinder 8 Misfire Detected).
Engine shudder, rough idle, and vibration caused by power imbalance between cylinders.
Noticeable loss of power and reduced throttle response, particularly under load.
Decreased fuel economy due to fuel trim adjustments and incomplete combustion on cylinder 8.
Occasional hesitation or stumble during steady cruising when cylinder 8 fires poorly.

How to diagnose P0284

A typical diagnostic flow when this code is present.

  1. 1
    Scan for all DTCs, document any companion P0308 misfire or fuel trim codes, and review freeze-frame data to identify operating conditions at time of fault.
  2. 2
    Inspect the cylinder 8 spark plug for fouling, erosion, cracks, or excessive gap; replace if worn and retest before proceeding.
  3. 3
    Test the cylinder 8 ignition coil output with a spark tester; swap with an adjacent coil and verify whether the fault follows the coil.
  4. 4
    Perform a cylinder contribution or balance test using a bi-directional scan tool to confirm cylinder 8 is the underperforming cylinder and that the PCM data is consistent.
  5. 5
    Inspect and test the cylinder 8 fuel injector: measure solenoid resistance, check connector integrity, and perform a flow balance test or swap to another cylinder position to determine if the fault is injector-specific.
  6. 6
    Conduct a compression test on cylinder 8 and compare to all other cylinders; perform a leak-down test if compression is more than 10% below the highest reading to identify valve, ring, or head gasket failure.
  7. 7
    Clear all codes after confirmed repairs, drive under conditions that match the original freeze-frame, and verify that crankshaft balance data for cylinder 8 returns to within specification.

Related powertrain codes

Frequently asked questions

Which engine types are affected by P0284?

Only engines with eight or more cylinders: V8, V10, V12, and I8 configurations. Cylinder 8 does not exist on four- or six-cylinder engines, so this code cannot be set by those platforms.

What is the difference between P0282, P0283, and P0284 for cylinder 8?

P0282 and P0283 are electrical faults — they report that the injector control circuit voltage is too low or too high, respectively. P0284 is a performance fault — it reports that cylinder 8 is not producing its expected power contribution, which can be caused by fuel, ignition, or mechanical failures entirely separate from an injector circuit voltage issue.

Can a bad spark plug really cause P0284?

Yes. A fouled, cracked, or excessively worn spark plug on cylinder 8 will produce incomplete or absent combustion on that stroke, reducing the crankshaft speed increment the PCM expects. This directly sets P0284 and is one of the least expensive causes to diagnose and resolve.

How serious is P0284 if compression on cylinder 8 is low?

Very serious. Low compression indicates internal mechanical damage — worn piston rings, damaged valves, or a failed head gasket. These conditions will worsen over time, potentially leading to complete cylinder failure, engine oil contamination from coolant ingress, and the need for a full engine rebuild or replacement if not addressed promptly.

Disabling P0284 in software

RaceTune can permanently disable P0284 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

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