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OBD-II Code

P0266

Severity

Not yet reviewed

Nobody on our side has assessed this code yet, so we are not going to guess at how serious it is.

Can you drive it

We cannot say

Treat it as unknown until a shop reads it with live data. If the check-engine light is FLASHING, stop driving as soon as it is safe to — that means an active misfire, whatever the code.

Indicative cost (USD)

$400–$7,000

From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.

P0266 means the ECM detected cylinder 2 contribution/balance fault — same diagnostic framework as P0263 but on cylinder 2.

How a shop works this

Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.

  1. Note every code that is set, not just this one.

    Codes that appear together usually narrow the cause faster than any one of them read alone.

  2. Read the freeze frame — the conditions the fault was recorded under.

    Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.

  3. Confirm the fault is current rather than history.

    Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.

  4. Then follow the diagnostic notes further down this page, in the order they are written.

    They are written in the order a shop works this code, cheapest checks first. Where they name a component, inspect its wiring and connector before replacing it.

If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.

Common symptoms

  • Check engine light
Read the full diagnostic procedureP0266 means the ECM detected cylinder 2 contribution/balance fault — same diagnostic framework as P0263 but on cylinder 2.

P0266 means the ECM detected cylinder 2 contribution/balance fault — same diagnostic framework as P0263 but on cylinder 2. The ECM measures crankshaft acceleration per firing event and per-cylinder injector balance rate, then flags cylinder 2 when its mm^3/stroke deviation pushes past the 2-5 mm^3 window or its contribution to crankshaft acceleration drops below roughly 85-92% of bank average.

Cheapest-first diagnostic ladder

  1. scan-tool the per-cylinder injector balance rate at warm idle — a cylinder 2 reading +/-4 mm^3/stroke or worse with the other cylinders within +/-1 mm^3 is the giveaway; positive deviation means the injector is over-fueling (stuck/dribbling) and the ECM is pulling fuel away, negative means under-fueling (clog/wear) and the ECM is adding fuel to compensate.
  2. Swap the cylinder 2 injector electrical connector with cylinder 3 (or any adjacent known-good cylinder), clear codes, and watch whether the balance fault migrates to the new cylinder — this isolates electrical from mechanical/hydraulic in 10 minutes.
  3. Return-flow test the injectors with calibrated bottles (target less than 50-100mL/min per injector at idle on most HPCR systems; a cylinder returning 200+ mL/min is stuck open).
  4. Relative compression test via scan tool starter-current monitor — variation greater than 15% from the highest-reading cylinder is mechanical (worn rings, valve leak, head gasket).
  5. On platforms with injector trim codes (most modern HPCR), confirm the trim/IQA code in the ECM matches the code etched on the injector — a swapped injector without recode causes balance faults all on its own. Expensive-misdiagnosis caveat: don't replace just the cylinder 2 injector on a high-mileage diesel — once one HPCR injector fails the rest are typically 80% to failure and the labor to drop and replace one (especially on LB7 Duramax under-the-valve-cover designs) is the same as doing all of them. Replacing one and being back in the bay in 30 days for cylinder 3 is a common shop-floor regret.
Vehicle-specific patterns2001-2004 GM Duramax LB7 throws P0266 along with the rest of the cylinder-balance family because the LB7 injectors fail as a set under the valve cove…
  • 2001-2004GM Duramax LB7 throws P0266 along with the rest of the cylinder-balance family because the LB7 injectors fail as a set under the valve cover — GM's extended 200k-mile warranty covered many; out of warranty, plan on a full-set replacement at $3,500-6,000.
  • 2003-2007Ford 6.0L Powerstroke throws P0266 from HEUI injector stiction or from low high-pressure oil pump output starving the injector hydraulically; IPR regulator and HPOP health must be confirmed before condemning injectors.
  • 2008-2010Ford 6.4L Powerstroke throws P0266 from Bosch piezo injector wear.
  • 2011-2016Ford 6.7L Powerstroke throws P0266 from CP4 contamination metal damaging injector nozzles.
  • 2003-2018RAM Cummins 5.9L/6.7L throws P0266 from Bosch CR injector wear; the inline-6 makes injector replacement relatively quick at ~6-8 hours labor.
  • 2007-2018Mercedes Sprinter OM642 3.0L V6 throws P0266 from piezo injector wear and from injector trim mismatch after replacement without coding.
  • 2009-2014Audi/VW TDI 2.0L throws P0266 from injector nozzle wear and CP4 metal contamination.

Estimated repair$400 to $7,000.

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