P0284 Code Meaning and Next Steps

First checks take 10 to 20 minutes for the first checks. No special tools are usually needed for the first checks.

Can you keep driving?

Stop driving if any of these apply

!The engine starts misfiring badly, stalling, or losing power sharply.
!The check-engine light flashes or the vehicle runs rough enough to risk catalyst damage.

If the light is steady and the vehicle still drives normally: Often yes for a short time, but it should not be ignored.

What to check first

Step-by-step checks

1
Free - no tools
Check whether P0284 appears with misfire, fuel-trim, or injector circuit codes
2
Free - no tools
Inspect the injector connector and harness for cylinder 8 for looseness, corrosion, or heat damage
3
Basic tool needed
Notice whether the engine roughness follows idle, load, or a specific temperature range
4
Basic tool needed
If scan data is available, compare cylinder 8 contribution with nearby cylinders before replacing parts
5
Basic tool needed
If the engine has a known compression issue, treat that as a serious clue rather than a side note

If the code returns

-If swapping ignition parts changes the fault, the ignition side moves higher on the list.
-If injector testing points to fuel delivery trouble, focus there before buying more parts.
-If the code returns after repair, repeat the contribution check before assuming another cylinder is bad.

Background

What this code means

P0284 is a generic OBD-II code for cylinder 8 contribution or balance fault.

That means the engine computer thinks cylinder 8 is not pulling its weight compared with the other cylinders.

Diagnosis

Common causes

Most common

Weak spark on cylinder 8

A plug, coil, or wire issue can reduce that cylinder's output.

Common

Injector imbalance

A restricted or weak injector can make the cylinder contribute less than the others.

Common

Compression problem

A mechanical issue can keep the cylinder from making normal power.

Possible

Connector or wiring fault

A poor connection can interrupt the injector or ignition circuit.

Avoid these mistakes

What not to do

xDo not replace injectors as a set before checking for wiring, fuel pressure, or a mechanical cylinder issue.
xDo not ignore drivability changes just because the code sounds like an injector balance fault.

Parts

Parts that may need replacing

PartTypical costNotes

Spark plug or ignition coil$20-$150Relevant when ignition testing points to cylinder 8.

Fuel injector$50-$250Worth checking if the injector is weak or restricted.

Compression or leakdown test$0-$150Needed if the mechanical side looks weak.

Related OBD codes

P0285

P0285 usually means cylinder 9 contribution or balance is lower than expected.

P0308

P0308 usually means cylinder 8 is misfiring.

P0300

P0300 usually means the engine is detecting random or multiple-cylinder misfires.

Source notes

Generic OBD-II (SAE J1979 / ISO 15031-5). P0284 was expanded around common cylinder 8 contribution faults, especially ignition weakness, injector imbalance, and compression problems.

This guide is written as a generic multi-make reference, so bulletin history, sensor locations, and repair order can still change by manufacturer and engine family.

This is generic OBD-II guidance and should not override vehicle-specific service information. Exact diagnosis and repair steps vary by make, engine family, and model year.

Last reviewed: 2026-04-10

Reference: Open reference

P0284 - P0284 Usually Means Cylinder 8 Contribution or Balance Is Lower Than Expected