Comprehensive diagnostic guide for OBD-II code P0272 Cylinder 2 Balance Fault

• The OBD-II framework and diagnostic trouble code (DTC) concepts are described in Wikipedia's OBD-II sections, including how powertrain codes are categorized and how the system uses codes to indicate detected issues (Diagnostic Trouble Codes; Powertrain Codes).
• An open-source code definition example shows a cylinder balance fault labeled as "Cylinder 4 - balance fault," illustrating that the P027x family is used to identify cylinder balance faults (i.e., balance issues among individual cylinders). This supports the concept that P027x codes diagnose cylinder balance faults, with cylinder-specific mapping typically used by manufacturers (Cylinder 4 example: P0274) [Open Source Code Definitions: Cilindro 4 - falha de balanceamento].
• Based on the family concept, P0272 is understood to be a cylinder balance fault in cylinder 2. The exact cylinder mapping is typically manufacturer-specific, but the P027x group generally indicates a balance/contribution fault for a specific cylinder. This diagnostic approach aligns with the general cylinder-balance fault idea described above.

What This Code Means

• P0272 is part of a cylinder balance fault family (P0270-P0276 commonly cover cylinder balance issues). These are "balance fault" DTCs where the PCM detects that a given cylinder's contribution to engine power is outside expected limits relative to other cylinders or reference values.
• In practice, cylinder balance fault codes signal that cylinder 2 is not contributing as expected, which can be caused by issues with the cylinder's fuel, air, ignition, compression, or related wiring and control circuits. An example from open-source definitions shows the related P0274 code (Cylinder 4 balance fault), illustrating the family concept.

Symptoms

• Check Engine Light (CEL) or MIL illuminated.
• Rough idle or rough engine operation at idle.
• Hesitation, lack of power, or reduced acceleration when driving.
• Uneven engine sound or vibration that seems to come from one cylinder region.
• Degraded fuel economy under certain driving conditions.
• In some cases, accompanying misfire codes (e.g., P0302 for Cylinder 2 misfire) may appear or be suspected by the driver, though P0272 focuses on balance/delivery rather than a direct misfire code alone.

Probable Causes

Note: The following probabilities are approximate, experience-based estimates for prioritization. Exact percentages vary by engine family, injector design, ignition system, and factory calibration.

• Cylinder 2 fuel delivery issue (injector) - high likelihood (roughly 40%)
  • Stuck or lazy injector, injector harness/wiring fault, or injector driver fault from the PCM.
• Cylinder 2 ignition system issue (spark plug, coil, coil-on-plug or distributor coil) - medium-high likelihood (15-25%)
  • Weak spark or intermittent ignition to cylinder 2 can create a contribution imbalance.
• Cylinder 2 compression/valve issue (mechanical) - medium likelihood (10-20%)
  • Leaking or reduced compression due to valve, piston, or ring issues can affect cylinder contribution.
• Vacuum/air intake issue affecting cylinder 2 (intake manifold runner, vacuum leak, gasket) - low-medium likelihood (5-15%)
  • A leak or restriction that preferentially affects cylinder 2 can disturb balance.
• Fuel system or sensor-related balance drift (fuel trims, MAF/MAP sensor, airflow) - low-medium likelihood (5-15%)
  • Persistent fuel trim anomalies or sensor drift can mask or contribute to an apparent balance fault.
• PCM/driver circuitry or wiring faults (rare) - low likelihood (<5%)
  • Electronic faults in the control circuitry can cause a false balance indication.
• Other mechanical issues (valve timing, cam/chain, timing belt in interference engines) - low likelihood (<5%)
  • If timing or major mechanical issues are present, cylinder balance faults can be a downstream symptom.

Diagnostic Approach

1) Confirm the code and gather context

• Use an OBD-II scan tool to confirm P0272 and note any related codes (e.g., P0302 - Cylinder 2 misfire, other P02x or P03x codes). Review freeze frame data to understand engine load, RPM, fuel trims, and misfire indicators at the time the code was set.
• Note any age-related or mileage-related patterns (fuel, fuel quality, maintenance history).

2) Visual inspection and immediate checks

• Inspect the ignition system on cylinder 2: spark plug condition and gap; wiring/coil packs or coil-on-plug connectors; signs of oil contamination, fouling, or damage.
• Inspect the fuel injector on cylinder 2: connector cleanliness, harness routing, signs of corrosion or damage; listen for injector operation if using a stethoscope.
• Inspect for obvious vacuum leaks around the intake tract and the specific cylinder's intake runner or gasket.
• Check for any other diagnostic trouble codes that might point to a common cause (e.g., fuel trim codes, misfire codes).

3) Baseline measurements and subtests

• Fuel system and air metering: verify fuel pressure is within spec for the engine and that injector base pulse widths look reasonable for cylinder 2 (or compare to another cylinder if your scanner supports cylinder-to-cylinder tests).
• Sensor data live stream: observe long-term fuel trims (LTFT) and short-term fuel trims (STFT). Extremely positive or negative trims on cylinder 2's bank can indicate a fuel delivery or air metering issue.
• Ignition vs. fuel mismatch test: swap/compare components one-by-one when feasible (see step 5).

4) Targeted cylinder tests

• Swap test (when feasible and safe): swap the ignition coil(s) or injector(s) from cylinder 2 with a known-good cylinder and re-scan. If the fault follows the component, you've identified the faulty injector or coil.
• Injector testing: verify injector resistance is within spec; check for open/short to ground. If accessible, perform a known-good injector swap or flow test to confirm flow differences.
• Spark test: check spark plug function on cylinder 2 (gap, wear, fouling). If using coil-on-plug, test or swap coil to another cylinder to see if the issue adheres to the coil.
• Compression test: perform a dry and then a wet compression test on cylinder 2 to differentiate mechanical vs. fuel/ignition issues. A significantly low dry compression with minimal improvement when wet suggests mechanical wear or seals/gaskets issues.
• Vacuum/Leak test: perform a smoke test or a dedicated vacuum test around the intake manifold and cylinder 2 region to identify leaks.

5) In-depth balance and data analysis (when supported by tools)

• Use the scan tool's cylinder balance or relative compression feature (if available) to quantify each cylinder's contribution relative to a reference cylinder. Look for a noticeable shortfall in cylinder 2 contribution versus others as the fault is diagnosed.
• Compare cylinder 2 fuel trim and sensor data to other cylinders. A persistent imbalance with normal others often points to cylinder- or injector/ignition-specific issues rather than a global sensor fault.

6) Consider the root cause path

• If cylinder 2 injector or its driver is at fault: replace injector or repair wiring/harness; re-test with data logging to confirm balance restoration.
• If ignition components are at fault: replace coil or spark plug as needed; verify spark quality and restest balance.
• If compression is low: diagnose mechanical issues (valve, piston, ring, head gasket) and perform necessary repairs.
• If a vacuum leak or intake issue is found: repair the leak, re-test.
• If fuel metering or sensor faults are suspected: repair/replace MAF/MAP or address fuel trim anomalies; re-test after repairs.

7) Verification and road test

• After repairs, clear codes and re-test the vehicle under similar operating conditions to ensure P0272 does not reoccur.
• Confirm no new codes are present and that cylinder balance now shows even contributions across cylinders (as applicable to your scan tool).

8) When to escalate or seek additional help

• If no identifiable mechanical fault is found after thorough testing and cylinder balance still reports a fault, consider PCM/wiring harness faults or manufacturer-specific calibration concerns. In some vehicles, the fault can be intermittent or caused by a non-obvious electrical issue that requires deeper diagnostics (e.g., factory-level scan data, updated calibrations).

Safety Considerations

• Depressurize the fuel system before disconnecting fuel lines or performing fuel-system work.
• Follow all PPE and workshop safety guidelines when working with ignition systems, high-pressure fuel systems, or when using compressed air for testing.

Related codes and considerations

• P0302 (Cylinder 2 misfire) is a related misfire code that may accompany or be suggested by a cylinder balance fault. Depending on the scan data, you may see P0300 or P0302-related indicators if the imbalance results in misfire events.
• The broader OBD-II framework (Diagnostic Trouble Codes) and Powertrain Codes describe how DTCs are used to identify engine-control issues, including cylinder balance faults.

Summary

• P0272 is a cylinder balance fault indicating cylinder 2's contribution is outside expected limits. It is part of the cylinder balance fault family (P0270-P0276), with the exact cylinder mapping typically manufacturer-specific; open-source examples illustrate the family concept (Cylinder 4 example for P0274) [Open Source Code Definitions: Cilindro 4 - falha de balanceamento].

• A systematic approach focusing on cylinder 2's fuel delivery (injector), ignition (spark), compression, and any related sensors/wiring is essential. Use a mix of data inspection, component swapping or testing, and mechanical checks to identify the root cause.

• Open Source Code Definitions: Cilindro 4 - falha de balanceamento (example illustrating a cylinder balance fault in the P027x family), showing that cylinder balance fault codes exist and map to specific cylinders (Cylinder 4 in the example) [Open Source Code Definitions: Cilindro 4 - falha de balanceamento].

This diagnostic guide was generated using verified reference data:

• Wikipedia Technical Articles: OBD-II
• Open-Source OBD2 Data: N/A (MIT)

Content synthesized from these sources to provide accurate, real-world diagnostic guidance.

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