P0284 – Cylinder 8 Contribution/Balance

P0284 is a diagnostic trouble code that points to a problem with cylinder number 8’s contribution or balance. In simple terms, your engine computer has detected that cylinder 8 is not pulling its weight compared to the others. This can be caused by fuel delivery issues, wiring faults, or a mechanical problem inside the engine. You may notice rough running, poor fuel economy, or a check engine light with reduced power. Understanding what this code means and how to approach it can save you money and prevent serious engine damage.

What Does P0284 Mean?

P0284 stands for “Cylinder 8 Contribution/Balance Fault.” Your ECU constantly monitors crankshaft speed and injector performance. When cylinder 8 doesn’t produce the expected power compared to the other cylinders, the ECU flags this imbalance and stores P0284.

This code is most often seen on V8 engines, especially diesel trucks, but it can appear on any engine that has a cylinder #8. The issue can be electrical (wiring, injector control), fuel-related (clogged or failing injector), or mechanical (compression loss, valve problem).

Quick Reference

• Code: P0284 – Cylinder 8 Contribution/Balance
• Severity: Moderate to high, especially if misfiring
• Common Causes: Faulty injector, wiring fault, low compression
• Typical Symptoms: Rough idle, loss of power, check engine light
• Risk: Possible engine damage or DPF issues if ignored (diesel)

Real-World Example / Field Notes

In the shop, I see P0284 most often on heavy-duty diesel pickups that tow or idle a lot. A common scenario: a 6.0L or 6.4L Power Stroke rolls in with a rough idle, check engine light, and heavy fuel smell. Scan tool shows P0284, sometimes with a generic misfire code. Power balance test clearly shows cylinder 8 lagging behind. In many cases, the root cause is a failing injector or high resistance in the injector harness near the valve cover. Once the injector and wiring are addressed, the truck smooths out immediately.

Symptoms of P0284

• Rough idle – Engine shakes or feels uneven when idling, especially when warm.
• Loss of power – Noticeable drop in acceleration or towing performance.
• Poor fuel economy – You use more fuel than usual for the same driving.
• Check engine light – MIL illuminated, often with only P0284 or with misfire codes.
• Engine vibration – Vibration felt through the steering wheel, seat, or pedals.
• Exhaust smoke – On diesels, possible white or gray smoke from unburned fuel.
• Hard starting – Longer crank time or rough start, especially cold.
• Reduced throttle response – Engine feels lazy or hesitant when you step on it.

Common Causes of P0284

Most Common Causes

• Faulty fuel injector #8 – Sticking, clogged, leaking, or electrically failing injector is the number one cause. The ECU sees low contribution because the cylinder isn’t getting the correct fuel.
• Injector wiring or connector issue – Broken wire, corrosion, loose connector, or high resistance in the injector circuit for cylinder 8 can cause erratic operation.
• Poor fuel quality or contamination – Water, debris, or low-quality fuel can partially block the injector or damage its internals.
• Low compression in cylinder 8 – Worn piston rings, valve issues, or head gasket leaks reduce cylinder pressure and therefore its contribution.
• ECU driver fault (rare but possible) – The injector driver circuit inside the ECU for cylinder 8 may fail, causing weak or no injector control.

Less Common Causes

• Intake air or boost leak near cylinder 8 – On turbocharged engines, a localized leak can lean out that cylinder’s mixture.
• Exhaust valve or seat damage – Burned valve or seat on cylinder 8 can cause low contribution without an obvious external noise at first.
• Incorrect injector coding or programming – On some modern diesels, injectors must be coded to the ECU. A wrong code for cylinder 8 can lead to imbalance.
• Aftermarket tuning issues – Aggressive tunes can highlight weak injectors or mask early problems until the ECU finally logs P0284.
• Mechanical timing issues – Rarely, a stretched timing chain or slipped gear affects valve timing enough to impact one cylinder more than others.

Diagnosis: Step-by-Step Guide

You’ll want a good scan tool (preferably with live data and power balance capability), a digital multimeter, basic hand tools, and if possible a fuel pressure gauge and compression tester. For diesels, access to Mode $06 data and manufacturer-specific tests is very helpful.

1. Confirm the code and check for companions. Scan the ECU for P0284 and any related misfire, injector, or fuel system codes. Multiple cylinder codes may point to a fuel supply issue rather than just cylinder 8.
2. Check freeze frame and live data. Look at when the code set (RPM, load, temperature). Use power balance or misfire counters to verify that cylinder 8 is indeed the weak one.
3. Visual inspection of wiring and connectors. Inspect the injector #8 harness, connectors, and valve cover pass-throughs (on many diesels). Look for chafed wires, broken clips, oil saturation, or corrosion.
4. Wiggle test. With the engine idling, gently move the injector 8 harness and connectors. If the idle changes or stumbles, you likely have an intermittent wiring fault.
5. Electrical tests on injector #8. With the key off, unplug injector 8 and measure resistance across the injector terminals. Compare with spec and with another known-good injector. Check for proper voltage supply and ground at the connector with the key on.
6. Swap test (if accessible). Where practical, swap injector 8 with another cylinder (for example, cylinder 6). Clear codes and test drive. If the code follows the injector (now P02xx for the new cylinder), the injector is bad.
7. Fuel system checks. Verify fuel pressure and quality. Look for signs of contamination in the fuel filter or rail. On diesels, pay attention to low-pressure and high-pressure sides.
8. Compression or cylinder leak-down test. If electrical and fuel checks pass, test compression on cylinder 8 and a neighboring cylinder. Low compression confirms a mechanical issue (rings, valves, head gasket).
9. Check Mode $06 and manufacturer tests. Some scan tools show contribution/balance data per cylinder in Mode $06. Use OEM-specific tests for power balance and injector buzz/actuation where available.
10. Evaluate ECU function. Only after ruling out injector, wiring, and mechanical issues should you suspect the ECU. Check for TSBs (technical service bulletins) about injector driver failures or updated calibrations.

Pro tip: Always fix any obvious wiring or connector issues before condemning an injector. Many “bad injectors” I’ve seen were actually high-resistance connections or broken wires hidden under harness tape.

Possible Fixes & Repair Costs

Repairs for P0284 depend on whether the problem is electrical, fuel-related, or mechanical. Typical costs vary by vehicle type (gas vs. diesel, light-duty vs. heavy-duty) and labor rates in your area.

• Repair or replace injector wiring/connector: $100–$350, depending on harness complexity and access.
• Replace fuel injector #8 (gasoline): $200–$500 parts and labor, more on some direct-injection engines.
• Replace fuel injector #8 (diesel): $400–$1,000+ per injector installed, especially on Power Stroke, Duramax, or Cummins engines.
• Fuel system cleaning / filter replacement: $80–$250 if contamination is minor.
• Mechanical engine repair (valves, compression issues): $800–$3,000+ depending on whether heads need to come off.
• ECU repair or replacement: $500–$1,500 including programming, but this is relatively rare.

Overall, you’re usually looking at $200–$1,200 for typical injector or wiring-related fixes, with costs climbing if internal engine damage is found. Access, engine layout, and whether you’re replacing one or multiple injectors all affect the final bill.

Can I Still Drive With P0284?

You can often still drive with P0284, but it’s not a great idea to ignore it for long. If the engine is running relatively smooth and the light is steady, driving short distances to a shop is usually okay. However, if the engine is shaking badly, smoking, or the check engine light is flashing, you should avoid driving and have it towed. Continued driving with a misfiring or underperforming cylinder can damage the catalytic converter, DPF (on diesels), or even the engine itself.

What Happens If You Ignore P0284?

Ignoring P0284 can turn a manageable repair into a major expense. A weak or misfiring cylinder can wash down cylinder walls with fuel, accelerate wear, overheat the catalytic converter or DPF, and cause excessive soot buildup. Over time, you may end up with burned valves, damaged pistons, or a clogged emission system that costs far more to fix than an injector or wiring repair would have.

Last updated: January 22, 2026

Vehicles Commonly Affected by P0284

P0284 is most frequently seen on V8 engines where cylinder 8 is at the rear of the engine, often harder to access and hotter. Commonly affected vehicles include Ford Power Stroke diesel trucks (6.0L, 6.4L, 6.7L), GM Duramax-equipped pickups, and Ram trucks with Cummins or Hemi V8 engines. It can also appear on gasoline V8 SUVs and performance cars from Ford, Chevrolet, GMC, Dodge, and some European brands. Any V8 with high mileage, heavy towing, or poor fuel quality is more likely to trigger this code.