P23FF: Bank 2 System B Air-Fuel Ratio Imbalance

P23FF mirrors P23FE for bank 2 and can only occur on V, W or boxer engines, because inline engines have no second bank. It means the cylinders on the side without cylinder 1 deviate from each other and the fault is assigned to injection system B, which on Ford's PFDI engines is the port path (lean and rich codes P2BF2/P2BF3). Bank-level monitors on such engines are documented, but under the general codes: GM's 2019 LT5 Corvette V8 fails bank 2 when the normalised oxygen sensor ratio exceeds 0.75, rated Type A and lighting the MIL on the first failed trip, and Ford sets P219B. No manufacturer publishes P23FF. When the fault stays confined to bank 2, the culprit usually sits on that side, such as a port fuel rail, a manifold gasket or several injectors of that bank.

Bank 2 is the side without cylinder 1, so it only exists on V or boxer engines.

Symptoms

• Check engine light on
• Fuel trims of the two banks clearly apart
• Possibly P2BF2 or P2BF3 as well

Most likely causes

• Several port injectors on bank 2 with deposits or wear
• Intake manifold gasket leaking on bank 2
• Supply problem in the port fuel rail feeding bank 2
• Front oxygen sensor or its wiring on bank 2 distorting the signal

What to check, in order

Start with the simplest. You can tick off each step.

1. See whether the light is flashing: if so, reduce engine load and avoid driving
2. Inspect the spark plugs, coils, and connectors
3. Swap the coil with another cylinder and see if the misfire moves with it
4. Check the injector and look for air leaks
5. Run a compression test if everything above checks out

Good to know

• Repair difficulty: medium
• It affects emissions.

What each character of P23FF means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 3: Ignition and misfires
• FF: Specific fault in that system

Frequently asked questions

Can I keep driving with code P23FF?

Avoid driving if the light is flashing or the engine is shaking: unburned gasoline can damage the catalytic converter.

What causes code P23FF?

The most common causes are: several port injectors on bank 2 with deposits or wear; intake manifold gasket leaking on bank 2; supply problem in the port fuel rail feeding bank 2.

Related codes

• P219BBank 2 Air-Fuel Ratio Imbalance
• P23FEBank 1 System B Air-Fuel Ratio Imbalance
• P2BF2Fuel Control System B Too Lean Bank 2
• P2BF3Fuel Control System B Too Rich Bank 2
• P23F9Cylinder 8 Injector B Air-Fuel Ratio Imbalance

Sources

• fordservicecontent.com: OBDSM2400OUTPUT 16Jul2024 WSM final V2 MCS7001
• gsi.ext.gm.com: 19OBDG03A Diagnostics
• law.cornell.edu: 13 CCR 1968.2

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.