Leaking or stuck-open fuel injector on cylinder 5 delivering too much fuel; Fault in the injector wiring, connector or driver circuit for cylinder 5; Fuel pressure too high, for example from a faulty regulator or pressure control fault; Fault in the sensor feeding the cylinder balancing, such as an exhaust oxygen or air-fuel sensor on that cylinder's bank, or a skewed reading; Contaminated or faulty air flow or manifold pressure sensor causing wrong fuelling calculation; Mechanical fault on cylinder 5 such as a vacuum leak at its intake runner or valve issue affecting the mixture reading; Outdated or faulty engine control unit calibration where a manufacturer bulletin describes this fault.

P02AB

Cylinder 5 - Fuel Trim at Min Limit.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
2: AreaFuel and air metering (injector circuit)
AB: FaultThe specific fault in that area

What it means

P02AB means the engine control unit has found that the individual fuel trim correction for cylinder 5 has reached its minimum limit, so it cannot remove any more fuel. The control unit sees that cylinder 5 is running richer than the others, or than the oxygen sensor data expects, and it has run out of range to lean it off. This code is set from cylinder-specific fuel trim data, so exact behaviour depends on the engine and its control strategy.

Symptoms

Engine management warning light on
Rough idle or a misfire-like shake
Smell of unburnt fuel from the exhaust
Higher than normal fuel consumption
Hesitation or uneven running under load
Black smoke or sooty exhaust tailpipe

Possible causes

Leaking or stuck-open fuel injector on cylinder 5 delivering too much fuellikely
Fault in the injector wiring, connector or driver circuit for cylinder 5possible
Fuel pressure too high, for example from a faulty regulator or pressure control faultpossible
Fault in the sensor feeding the cylinder balancing, such as an exhaust oxygen or air-fuel sensor on that cylinder's bank, or a skewed readingpossible
Contaminated or faulty air flow or manifold pressure sensor causing wrong fuelling calculationrare
Mechanical fault on cylinder 5 such as a vacuum leak at its intake runner or valve issue affecting the mixture readingrare
Outdated or faulty engine control unit calibration where a manufacturer bulletin describes this faultrare

How to diagnose

Read all stored and pending codes and note freeze frame data such as load, engine temperature and fuel trim values
Check for other fuel trim, misfire or oxygen sensor codes that point to a shared cause
Inspect the cylinder 5 injector connector and wiring for damage, corrosion, or poor pin tension
Look at live data for short and long term fuel trims and any cylinder-specific trim values to see whether the problem is only on cylinder 5
Check fuel pressure against the manufacturer's specification and check for fuel in the vacuum line of the regulator, where fitted
Test the cylinder 5 injector resistance and operation, and check the injector spray pattern and leak-down, following the manufacturer's procedure
Check the oxygen or air-fuel sensor signals and the air flow or manifold pressure sensor readings for plausibility
Look for a manufacturer calibration update or technical bulletin for the specific model and engine

How to fix

Replace or professionally clean and flow test the leaking cylinder 5 injector as the testing indicates
Repair or replace damaged injector wiring or connectors
Correct fuel pressure faults by repairing or replacing the faulty regulator or pressure control component, depending on the fuel system design
Replace a faulty oxygen, air-fuel, air flow or manifold pressure sensor once testing confirms it is at fault
Repair any intake or mechanical fault found on cylinder 5
Apply a manufacturer-released control unit calibration update only where it is a documented fix for this fault

Can I keep driving?

Medium severity

The car can usually be driven for a short time, but an over-rich cylinder can wash oil from the bore and overheat the catalytic converter, so get it checked soon. If it runs very roughly, smells strongly of fuel or the warning light flashes, stop driving and have it inspected.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.