P230B

Code

Generic P — Powertrain

Cylinder 2 Air-Fuel Ratio Imbalance - Adjustment At Limit During Balance

Brand: Generic

Type: P — Powertrain

Views: UK: 23 EN: 38 RU: 19

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Page language: EN

Causes

Faulty or clogged fuel injector at cylinder 2
Injector driver or wiring open/short/intermittent
Low or high fuel pressure (fuel delivery problem)
Intake manifold leak or vacuum leak near cylinder 2
Poor compression (worn rings, valves, head gasket) on cylinder 2
Ignition issue on cylinder 2 (weak spark, faulty coil, plug, or wiring)

Symptoms

Check Engine Light / MIL illuminated
Rough idle or vibration
Cylinder-specific misfire or reduced power under load
Poor fuel economy
Possible elevated hydrocarbon emissions or failed emissions test

What to check

Read stored freeze frame and pending codes; note fuel trim and O2/wideband readings when code set
Check for related DTCs (misfire codes, injector circuit codes, fuel system codes, O2 sensor codes)
Monitor live data: per‑cylinder contribution/correction, short‑ and long‑term fuel trims, O2/wideband readings, injector pulse width
Check misfire counters for cylinder 2 (P0302 or cylinder 2 count)
Inspect wiring and connectors for injector and O2/wideband sensors for damage or corrosion
Perform a fuel pressure/flow test to verify rail pressure within specification

Signal parameters

Short Term Fuel Trim (STFT) for bank/cylinder: should generally be within ±10% (excessive values indicate correction limit reached)
Long Term Fuel Trim (LTFT): large positive or negative values (>±10–15%) indicate systemic lean/rich conditions
Cylinder contribution/correction value for cylinder 2: large corrective value at or near limit indicates problem
O2 sensor voltage (narrowband): ~0.1–0.9 V switching in closed loop; slow or stuck values are suspect
Wideband lambda/AFR: target ≈14.7:1 (stoichiometric) for gasoline; deviation indicates fueling error
Injector pulse width and duty cycle: compare commanded width to other cylinders

Diagnostic algorithm

Verify code and capture freeze frame. Note engine load, RPM, fuel trims, O2/wideband values and fuel pressure when code set.
Scan for additional or related DTCs (P0302, P0202, P0171/P0174, O2 sensor codes) and address higher‑priority faults first.
Monitor live data while engine is warmed up and in closed loop: watch cylinder 2 contribution/correction, STFT/LTFT, O2/wideband response and injector pulse widths.
Inspect wiring/connectors for cylinder 2 injector and nearby sensors (O2, MAF, MAP). Repair any damaged wiring or poor connections.
Verify fuel rail pressure and regulator function under static and loaded conditions. Replace or repair fuel delivery components if out of spec.
Confirm injector function: back‑probe injector connector for proper drive, check injector resistance, use a noid light or scope to verify waveform and pulse; consider swapping injectors with another cylinder to see if imbalance follows injector.
Perform a wet and dry compression test or leak‑down test on cylinder 2 to rule out mechanical issues (rings, valves, head gasket).
Check for intake manifold or vacuum leaks near cylinder 2 with a smoke test or careful inspection.
Test O2/wideband sensors for correct response time and output. Replace sensor if out of specification or if wiring is faulty.
After repairs or component replacements, erase codes and re-run cylinder balance/cylinder contribution tests and verify trims and AFR return to normal. If code returns, capture new data and escalate to PCM-level diagnostics or manufacturer technical service information.

Likely causes

Leaking or clogged injector limiting correct fuel metering for cylinder 2
Cylinder mechanical fault (low compression or valve sealing) causing poor combustion
Vacuum leak or intake gasket leak near cylinder 2 introducing extra air
Faulty AFR/O2 sensor or wiring giving incorrect feedback so PCM limits correction

Fault status

⚠️ Status

Cylinder 2 air‑fuel ratio imbalance — PCM reached adjustment limit during cylinder balance/compensation. Inspect fueling, ignition, compression, intake leaks, and AFR sensing for cylinder 2.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.5-3.0 hours