What P0266 means
P means powertrain (engine and transmission). The 0 marks a generic code defined by SAE, so the same number means the same thing across makes. The third character, 2, places it in the fuel and air metering, injector circuits subsystem; the last two digits identify the specific fault.
Each fuel injector is a solenoid switched by a driver in the engine computer. The module watches the electrical behaviour of every injector circuit and, on many engines, how much each cylinder contributes to engine speed. A cylinder-specific code narrows the fault to one injector, its wiring or its driver.
Cylinder numbering is set by the manufacturer, so check the cylinder layout for your engine to find cylinder 2; it is not always the one nearest the timing belt or chain.
What “Contribution/Balance” means here
A contribution or balance fault means cylinder 2 is adding more or less to engine speed than the others, judged by crankshaft speed changes. On diesels the module may already be adjusting that injector's quantity and has run out of correction. Injector flow, injector wiring and that cylinder's compression are the main suspects.
What you may notice
Symptoms depend on the vehicle and on how the module responds to the fault. Any of these can accompany P0266:
- Misfire on the affected cylinder
- Rough idle and loss of power
- Fuel smell or smoke if an injector sticks open
- Higher fuel use
Where to start diagnosing P0266
- Inspect the injector connector and harness for the affected cylinder; fuel-soaked or heat-damaged connectors are common.
- Measure injector coil resistance and compare with specification and with the other injectors.
- Use a noid light or scope to confirm the injector is being pulsed.
- Swap the injector to another cylinder where practical and see if the fault follows it.
Clear the code only after recording freeze frame data: it shows the engine speed, load and temperature at the moment the fault set, which is often the best clue to reproducing it.
Live data to watch
These standard OBD2 values relate to P0266. Support varies by vehicle; a value your car does not report will simply be missing.
| Value | What to look for |
|---|---|
| Engine RPM (PID 0x0C) | Unstable idle speed is a sign of an inactive cylinder. |
| Short and long term fuel trim (PIDs 0x06–0x09) | A dead injector usually drives trims lean. |
| Misfire counts | Available through Mode 06 on many vehicles; shows which cylinder is misfiring. |
Related codes
Codes from the same fuel injector circuit family. If several are stored together, the shared part — wiring, a common reference voltage, or the component itself — is the place to start.
| Code | Definition |
|---|---|
| P0202 | Injector Circuit Malfunction - Cylinder 2 |
| P0262 | Cylinder 1 Injector Circuit High |
| P0263 | Cylinder 1 Contribution/Balance |
| P0264 | Cylinder 2 Injector Circuit Low |
| P0265 | Cylinder 2 Injector Circuit High |
| P0267 | Cylinder 3 Injector Circuit Low |
| P0268 | Cylinder 3 Injector Circuit High |
| P0269 | Cylinder 3 Contribution/Balance |
Further reading
Frequently Asked Questions
What does P0266 mean?
P0266 is the generic SAE J2012 code for "Cylinder 2 Contribution/Balance". In plain terms, it means the engine computer's fuel injector circuit monitor has reported "Cylinder 2 Contribution/Balance".
Can I keep driving with P0266?
A cylinder that is not firing can overheat the catalytic converter. Limit driving and avoid high loads until it is fixed.
What should I check first for P0266?
Inspect the injector connector and harness for the affected cylinder; fuel-soaked or heat-damaged connectors are common.
Definition source: SAE J2012 / ISO 15031-6 generic DTC definitions. This is the generic meaning that applies across makes; a manufacturer can define a code more narrowly or add its own sub-codes, so confirm against the service information for your vehicle before replacing parts. Written by the OBDAssistant engineering team — see our editorial policy.