P0266: How to Diagnose & Fix — Cylinder 2 Contribution/Balance Fault
4 vehicles · 3 makes · $400-$5,000 repair
How to diagnose and fix P0266: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
SEAT Leon · 2005–2010
The BKD 2.0 TDI Pump-Düse engine in Leon Mk2 (and Golf Mk5, Passat B6, Audi A3 8P) suffers PD injector failure, particularly on long-life servicing. Failure modes: misfire on one cylinder, hard starting, white smoke, sooty exhaust. Often accompanied by cracked cylinder head between #2 and #3 due to local overheating.
Common Symptoms
- misfire cold
- hard start
- white smoke
- rough idle
How to Fix
Single injector replacement €400-€700 incl. coding. Full set (4) €1,400-€2,000. If head crack present, head rebuild adds €1,200-€2,000 more. Use VW 507.00 oil at 10,000 km max, NOT long-life intervals.
GMC Sierra 3500HD · 2015–2024
The Bosch piezoelectric fuel injectors on the Duramax L5P and LML engines can fail due to contaminated fuel, high-mileage wear, or internal electrical faults. A failed injector causes white smoke on startup, rough idle, misfires on the affected cylinder, and fuel dilution of the engine oil. The high fuel rail pressures (up to 36,000 PSI on the L5P) stress the injectors over time. Contaminated fuel from bulk diesel stations accelerates injector wear.
Common Symptoms
- White or gray smoke on cold start
- Rough idle or misfire on one or more cylinders
- Fuel smell in engine oil (fuel dilution)
- Check engine light with injector circuit codes
- Reduced power and poor fuel economy
- Hard starting in cold weather
How to Fix
Diagnose the failed injector with a relative compression test and injector balance rate scan using a Tech 2 or equivalent scan tool. Replace the failed injector(s) — OEM Bosch injectors are $300-$500 each, and labor is 2-4 hours per injector ($300-$600). Always replace the injector hold-down clamp and fuel return line seals. If one injector fails at high mileage, consider replacing all 8 as the others are likely near end of life. Use a quality fuel additive like Stanadyne or Hot Shot Secret to protect remaining injectors.
Sources for this issue (1)
Ford F-350 · 2003–2007
The 6.0L Power Stroke uses hydraulically actuated, electronically controlled unit injectors (HEUI) that are fired by high-pressure engine oil. Oxidized oil leaves a varnish film on the injector spool valve, and when the engine is cold that film creates static friction (stiction) that keeps the spool from moving on command. The result is a dead or lazy cylinder for the first minutes after a cold start, clearing as oil warms. Owners report a rough, shaking cold start that smooths out after several miles and then progressively worsens over months until the injector fails outright. Extended oil-change intervals, low-quality oil and short-trip use all accelerate it. This is an oil-side failure mode of the HEUI system and does not apply to the 6.4L or 6.7L, which use common rail.
Common Symptoms
- Very rough shaking idle for the first 1-5 minutes after a cold start
- White or gray smoke on cold start
- Misfire that disappears once the engine warms
- Loss of power
- Injector contribution numbers out of range on a scan tool
How to Fix
Confirm with a scan tool by watching injector contribution/cylinder balance and injector on-time when cold. Short-term mitigation is switching to a quality oil of the correct grade, shortening the oil change interval, and using a block heater in cold weather; ester-based stiction additives are widely used in the community and sometimes recover a marginal injector. The real repair is removing the valve covers and replacing the affected injectors (often all eight, since they age together) along with the injector O-rings and, on higher-mileage engines, the high-pressure oil system standpipes and dummy plugs. No recall applies.
Sources for this issue (3)
Ford F-250 Super Duty · 2003–2007
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P0266 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0266 mean?
P0266 stands for "Cylinder 2 Contribution/Balance Fault." P0266 is a generic powertrain code indicating the engine computer detected that cylinder 2 is not contributing its expected share of power, meaning its output is unbalanced compared to the other cylinders. The PCM monitors crankshaft acceleration and fuel/injector behavior per cylinder, and an imbalance here often signals a misfire, fuel-delivery, or mechanical problem specific to cylinder 2. Left unaddressed, this can cause rough running, poor performance, and possible catalytic converter damage.
What are the most common causes of P0266?
The most common causes of P0266 are: Faulty or clogged fuel injector on cylinder 2, Injector wiring or connector fault, Ignition fault (coil, plug) causing a cylinder-2 misfire, Low compression / mechanical issue (valve, ring) on cylinder 2, Vacuum or intake leak affecting that cylinder, Contaminated or restricted fuel supply, PCM driver circuit fault for that injector. The specific cause varies by vehicle.
How much does it cost to fix P0266?
Repair costs for P0266 range from $400 to $5,000, depending on the vehicle and root cause.
Which vehicles are affected by P0266?
Au7o has documented P0266 across 4 vehicle models from 3 manufacturers: Ford, GMC, SEAT.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.