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DTC codes / P23xx · Ignition system and misfire / P230A

P230ACylinder 1 Air-Fuel Ratio Imbalance Adjustment At Limit During Balance

P230A means the powertrain control module (PCM) has been trimming the fuel delivery to cylinder 1 to correct an air-fuel ratio imbalance, and that trim has reached its calibrated limit during a balance test. In plain terms, cylinder 1 is not contributing its fair share of power, and the computer can no longer compensate by adding or subtracting fuel.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyProfessional
AreaIgnition system and misfire

Symptoms you may notice

  • Illuminated check engine light, often with no other noticeable symptoms
  • Rough idle or a noticeable shake that is worse when the engine is cold
  • Misfire-like shudder or hesitation during acceleration
  • Slightly reduced fuel economy over time
  • A faint fuel or exhaust smell if the cylinder is running rich
  • In some cases, a flashing check engine light if the imbalance is severe enough to risk catalytic converter damage

Common causes, most likely first

  1. Faulty or clogged fuel injector on cylinder 1, delivering too much or too little fuel
  2. Vacuum leak at the intake manifold runner or injector O-ring specific to cylinder 1
  3. Worn or misadjusted valve train on cylinder 1, such as a tight valve clearance or collapsed lifter
  4. Low compression on cylinder 1 from worn rings, a scored bore, or a leaking head gasket
  5. Contaminated or failing spark plug or ignition coil on cylinder 1 causing incomplete combustion
  6. Leaking intake manifold gasket affecting only the cylinder 1 runner
  7. Exhaust leak before the oxygen sensor that skews the balance reading for that cylinder

How to diagnose and fix it

  1. Scan all modules and record freeze-frame data, then check for related misfire or fuel trim codes before touching any parts
  2. Perform a cylinder balance test or compression test on cylinder 1 and compare it with the other cylinders
  3. Inspect the spark plug and ignition coil on cylinder 1 for fouling, wear, or a weak spark
  4. Check for vacuum leaks at the intake runner and injector O-ring using a smoke machine or carburetor cleaner
  5. Measure fuel injector resistance and, if equipped, perform an injector flow test or swap the injector to another cylinder to see if the code follows
  6. Run a running compression test or leak-down test on cylinder 1 to rule out valve or ring sealing problems
  7. Repair the confirmed mechanical or fuel-delivery fault, clear the codes, and verify the balance test now passes with no pending codes

What the balance test is really telling you

  • This code is set by a dedicated cylinder balance test that the PCM runs under specific conditions, so it can appear even when the engine feels normal to the driver.
  • A dirty or failing injector on cylinder 1 is the most common cause, but technicians often replace all injectors before confirming which one is actually at fault.
  • A vacuum leak at the intake runner for cylinder 1 can mimic a bad injector because the extra unmetered air leans out that cylinder only.
  • Low compression from a tight valve clearance is easy to miss because the engine may idle smoothly and only set the code during the balance test.
  • Do not assume the oxygen sensor is bad just because a fuel trim code is stored; the sensor is usually reporting a real imbalance rather than causing it.

Can I keep driving with P230A?

You can usually drive the vehicle short distances to a repair shop, but avoid hard acceleration and heavy loads until the fault is diagnosed. If the check engine light flashes or the engine runs very rough, stop driving to prevent catalytic converter damage.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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