OBD-II Code P0266 — What It Means & How to Fix It

What Does This Error Mean?

P0266 means Cylinder 2 is not contributing its fair share of engine power. The engine computer tracks how much power each cylinder produces, and Cylinder 2 came up short. This is called a contribution or balance fault. The cylinder is firing, but doing less work than the others. You may feel vibration, rough idle, or reduced power — especially at low speeds.

Affected Models

All vehicles 1996+
Common in GM, Ford, Chrysler multi-cylinder engines
Common in Toyota and Honda four-cylinder and V6 engines
Common in high-mileage vehicles with worn injectors
Frequent in vehicles that haven't had recent tune-up maintenance

Common Causes

Partially clogged fuel injector on Cylinder 2 delivering insufficient fuel
Weak spark from a worn or fouled spark plug on Cylinder 2
Failing ignition coil providing inadequate energy to fire Cylinder 2
Low compression in Cylinder 2 from worn rings or valves
Small vacuum leak near the Cylinder 2 intake runner leaning out that cylinder

How to Fix It

Start by inspecting and replacing the Cylinder 2 spark plug. A worn, cracked, or oil-fouled plug produces weak combustion — exactly what a contribution fault describes. Check the plug condition carefully when removing it.

A black sooty plug suggests rich fuel; a white chalky plug suggests lean; oil on the plug suggests internal engine wear.
Test the ignition coil for Cylinder 2 by swapping it with a coil from a different cylinder. Clear the codes and drive briefly. If the P0266 moves to the swapped cylinder's code number, the coil is the problem.

This swap test is the fastest and cheapest way to confirm a coil fault without buying anything.
Have the Cylinder 2 fuel injector cleaned or flow-tested. A partially clogged injector delivers fuel unevenly, causing weak combustion without triggering a full misfire code.

Injector cleaning services run $50–$100 per injector at most shops. It's worth trying before buying a replacement.
Inspect around the Cylinder 2 intake port for vacuum leaks. A small crack or loose hose allowing extra air into just one cylinder makes it run lean and reduces power output.

Spray carburetor cleaner around intake runners with the engine running. A change in idle RPM near any spot reveals a leak.
If the above steps don't resolve it, do a cylinder compression test. Cylinder 2 should read within 10% of the other cylinders. Low compression points to internal engine wear.

A wet compression test (with a small amount of oil added) helps confirm whether worn rings or valves are the cause.

When to Call a Professional

If new spark plugs and a coil swap don't help, and injector cleaning didn't change things, compression is your next step. A compression test will tell you if there's internal engine wear. Low compression means engine work — valve jobs, ring replacement, or head gasket repairs. Those repairs typically range from $1,000 to $4,000+ and require a qualified mechanic.

Frequently Asked Questions

What's the difference between P0266 and P0302?

P0302 is a misfire — Cylinder 2 completely failed to fire on one or more engine cycles. P0266 is a contribution fault — Cylinder 2 fired, but produced noticeably less power than expected. Contribution faults are often an early warning sign of the same problems that eventually cause misfires. Catch and fix P0266 early, and you may prevent P0302 from ever appearing.

Can I fix P0266 myself?

Yes, often you can. Replacing spark plugs and swapping ignition coils are DIY-friendly repairs that any careful beginner can handle. Injector cleaning is also straightforward. If those don't work, a compression test requires a basic gauge available at any auto parts store. Only internal engine repairs — rings, valves, head gaskets — require a professional mechanic.

How much does P0266 cost to fix?

Spark plug replacement: $50–$150 for a full set. Ignition coil: $50–$200 installed. Injector cleaning: $50–$100 per injector. Injector replacement: $150–$400 installed. Compression/engine repairs: $1,000–$4,000+ for internal engine work.