P0266
Cylinder 2 Contribution/Balance
If your code reader dashboard displays the generic DTC error code P0266, your vehicle is currently experiencing an active failure related to "Cylinder 2 Contribution/Balance". Proper system troubleshooting is required to safely clear this warning.
Driver's Summary
Your vehicle's computer logged P0266 after detecting a malfunction in the cylinder 2 contribution/balance system. On the road, this usually shows up as vibration under acceleration, poor fuel economy. This is a serious fault — avoid extended driving and have your vehicle inspected by a mechanic as soon as possible to prevent further damage.
Symptoms
Vibration under acceleration, poor fuel economy
Common Causes
- Defective fuel injector on Cyl 2
- Bad ignition coil
- Intake manifold leak
- Low compression
How to Fix
- 1 Replace fuel injector
- 2 Replace ignition coil
- 3 Check for intake leaks
- 4 Perform leak-down test
Technical Explanation
The PCM triggers P0266 after its internal monitoring routine detects that a specific circuit or sensor has exceeded its acceptable operating range. The PCM monitors crankshaft rotational velocity via the CKP sensor at a resolution of individual tooth gaps on the reluctor ring. A combustion event in each cylinder produces a measurable acceleration spike; its absence or weakness is flagged as a misfire event within a 200-revolution or 1000-revolution test window. After two failed drive cycles, the code transitions from a pending to a confirmed DTC, and the PCM activates the MIL. Clearing the code without repairing the fault will result in re-illumination within one to two complete drive cycles.
Is It Safe to Drive?
This fault carries real mechanical risk. The root causes — including defective fuel injector on cyl 2 — can trigger a chain reaction of component failures if the vehicle continues to be driven. Have it towed or drive directly to a shop without delay.
Mechanic's Pro Tip
For P0266, always perform a smoke test before replacing any parts — unmetered air from a cracked intake boot, split hose, or failed gasket is the root cause in the majority of lean fault cases and costs almost nothing to fix. After any repair, clear the code and watch short-term fuel trim (STFT) live on a scan tool; it should recover to within ±5% at idle within 2–3 minutes if the vacuum leak is truly resolved.
Injector: 150 - 400