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-250 Super Duty · 2003–2007
Each 6.0L HEUI injector contains two spool valves actuated by high-pressure engine oil. Oil varnish, coking and wear cause the spool to stick - 'stiction' - so the injector cannot respond to the FICM's command quickly enough. The signature is unmistakable to owners: a hard cold start followed by a shaking, misfiring, smoky idle for the first few minutes that disappears once the oil warms and thins. Cylinder contribution and injector on-time data will show one or more cylinders far out of range. Extended oil change intervals and the wrong oil grade accelerate it, and the 6.0's oil is doing double duty as hydraulic fluid, which is why oil quality matters far more here than on a conventional diesel.
Common Symptoms
- Hard cold start
- Rough misfiring idle when cold that clears once warm
- Excessive white or gray smoke on startup
- Random cylinder misfire codes
- Loss of power and poor fuel economy
How to Fix
Confirm with a scan tool (cylinder contribution / injector buzz test) and check FICM voltage first, since a weak FICM mimics stiction exactly. Mild cases sometimes improve with a stiction-eliminator additive and a fresh oil change on the correct grade, but this is a band-aid. The real fix is remanufactured injectors, and they should be replaced as a full set of eight because the labor - valve covers and high-pressure oil rails off - is the bulk of the cost. Shorten oil change intervals afterward.
Sources for this issue (3)
Ford F-350 · 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.