P23FE: Bank 1 System B Air-Fuel Ratio Imbalance

P23FE reports a cylinder-to-cylinder imbalance on bank 1 that the control unit attributes to fuel system B, without naming a cylinder. Ford's 2024 OBD summary explains the letter for its dual-injection engines: the port path is Fuel Control System B with its own lean and rich codes (P2BF0/P2BF1 for bank 1), while direct injection forms system A. Ford's imbalance monitor itself still stores only P219A: it runs once per trip in closed loop after the fuel monitor has adapted, needs 300 to 700 s and fails above an imbalance ratio of 0.75. No manufacturer publishes P23FE. An inline engine has only bank 1, so the code then covers all its cylinders; on V engines it is the side with cylinder 1. A system-wide B code points to the port rail, its pressure or several port injectors at once.

Bank 1 is the side of the engine with cylinder 1. Inline engines only have this bank.

Symptoms

• Check engine light on
• Lean or rich fuel trim on bank 1, possibly P2BF0 or P2BF1
• Slightly increased fuel consumption

Most likely causes

• Several port injectors on bank 1 fouled by deposits
• Port fuel rail pressure or low-pressure supply wrong on bank 1
• Intake manifold leak on the bank 1 side
• Front oxygen sensor of bank 1 responding poorly

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 P23FE means

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

Frequently asked questions

Can I keep driving with code P23FE?

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

What causes code P23FE?

The most common causes are: several port injectors on bank 1 fouled by deposits; port fuel rail pressure or low-pressure supply wrong on bank 1; intake manifold leak on the bank 1 side.

Related codes

• P219ABank 1 Air-Fuel Ratio Imbalance
• P23FFBank 2 System B Air-Fuel Ratio Imbalance
• P2BF0Fuel Control System B Too Lean Bank 1
• P2BF1Fuel Control System B Too Rich Bank 1
• P23F2Cylinder 1 Injector B Air-Fuel Ratio Imbalance

Sources

• fordservicecontent.com: OBDSM2400OUTPUT 16Jul2024 WSM final V2 MCS7001
• 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.