Share a caseSign in
FuelSeverity Medium: diagnose soon

P0266Cylinder 2 Contribution/Balance

What it means

The ECU measures how much each cylinder speeds up the crankshaft. Cylinder 2 contributes clearly more or less than the others, and the correction needed to balance it is beyond the limit. On diesels this is usually an injector or a compression problem.

Symptoms

  • Rough or shaking idle
  • Hard start, sometimes with smoke
  • Knocking from one cylinder

Common causes

  • Worn or leaking injector on cylinder 2
  • Low compression on cylinder 2 (rings, valve)
  • Leaking injector copper seal
  • Air in the fuel or low fuel supply pressure

What to check first

  1. Read the injector correction (balance) values at warm idle
  2. Run a leak-off (return flow) test on all injectors
  3. Run a compression or relative compression test before replacing an injector
Can I drive with P0266? Usually yes for a short distance, but performance or economy may suffer and the fault can get worse. Diagnose it soon.
Practise it: Worn injector, cyl. 2 (diesel) in the engine simulator shows this fault in live data, tests and on the scope.Open in the simulator

Generic OBD-II meaning. Manufacturer-specific meanings and checks can differ; always check the service information for the car.

How to test the parts behind P0266

Common-rail diesel injectorWiring, typical values, multimeter and scope tests

Known engine problems that set P0266

2.0 TDI EA189: Injector wear and leakageVolkswagen, Audi, Skoda, Seat · typically 150,000–300,000 km1.6 TDI EA189: Leaking or worn injectorsVolkswagen, Audi, Skoda, Seat · typically 120,000–250,000 km1.5 dCi K9K: Injector failure and starting problemsRenault, Dacia, Nissan, Mercedes-Benz, Suzuki · typically 100,000–250,000 kmMercedes OM651: Injector failure on early engines (Delphi piezo)Mercedes-Benz · typically 40,000–150,000 km

Cases with P0266 (1)

Share yours
Long crank when warm and white smoke for a few secondsTraining case · 2011 Volkswagen Golf VI · 1.6 TDI (CAYC) · fixed: Injector no. 2 worn internally: too much leak-back while running and dripping in

Colleagues asking about P0266

Ask for help

Stuck on P0266? Describe what you measured and ask the community.

P0266: questions and answers

What does P0266 mean?

P0266: Cylinder 2 Contribution/Balance. The ECU measures how much each cylinder speeds up the crankshaft. Cylinder 2 contributes clearly more or less than the others, and the correction needed to balance it is beyond the limit. On diesels this is usually an injector or a compression problem.

What are the symptoms of P0266?

Rough or shaking idle. Hard start, sometimes with smoke. Knocking from one cylinder.

What causes P0266?

Worn or leaking injector on cylinder 2. Low compression on cylinder 2 (rings, valve). Leaking injector copper seal. Air in the fuel or low fuel supply pressure.

How do you diagnose P0266?

1. Read the injector correction (balance) values at warm idle 2. Run a leak-off (return flow) test on all injectors 3. Run a compression or relative compression test before replacing an injector

Can I drive with P0266?

Usually yes for a short distance, but performance or economy may suffer and the fault can get worse. Diagnose it soon.